COMPUTER SYSTEM
FIELD OF THE INVENTION

5 The present invention relates to a computer system such
as a control controller used foraplantmonitor control system
that monitors and controls, e.g., a water and sewage plant.
BACKGROUND OF THE INVENTION
10 In recent years, computers used as plant monitor control
systems have larger memory capacities and processors with
improved operation capabilities. Therefore, fast operations
are achievable usingoperationprogramswithlarge capacities.
Especially, each of control controllers including PLCs
15 (programmable logic controllers) can monitor and manipulate
many control devices alone. Also in view of maintenance of
plants, cost reduction and high efficiency are in progress.
Patent Document 1 includes the background of this
technical field. Patent document 1 proposes, in a control
20 controller provided with chargeable backup means, a volatile
main memory, and a nonvolatile backup memory for backup of
initial parameters of the main memory, means which transfers
the parameters from the backup memory to the main memory in
accordance with duration of a power outage.
25 Thus, in Patent Document 1, continuous and stable
2
operation is possible even after a power outage.
[Prior Art Documents]
[Patent Documents]
5 [Patent Document 11
JP-A NO. 1993-53932
Thus, acontrolcontrollerhavingchargeablebackupmeans
is prerequisite for application of the technique of Patent
Document 1. For this reason, a control controller without
10 chargeable backup means may need another means. Chargeable
backupmeansincludesaprimarybatteryandasecondarybattery.
In accordance with an environment of an installation site for
the control controller, it may be difficult to connect these
batteries to the controller. As a result, the usefulness of
15 the nonvolatile memory is reduced.
Thus, in actuallyconfiguring anddeliveringthe control
controller, the measure against a power outage was needed to
be changed or the configuration of the control controller was
needed to be devised in accordance with the presence of
20 installation of the chargeable backup means.
It is desirable to provide a computer system capable of
achieving means that executes control programs independently
of the presence of chargeable backup means.
25 SUMMARY OF THE INVENTION
A computer system in the present invention includes a
memory unit having a nonvolatile memory and a volatile memory
and a processing unit to execute control programs described
in control program tables ofthe memory unit. The nonvolatile
5 memory includes a first control program table. The volatile
memoryincludesasecondcontrolprogramtable. Uponpower-up,
whether rechargeable backup means is present and whether the
first control program table or second control program table
is preferentially used are confirmed. When there is no
10 connectionofthechargeablebackupmeansandthesecondcontrol
programtable is used, the content ofthe first control program
table is transferred tothe second control programtable. The
content of the second control program table is transferred to
the first control program table at each predetermined control
15 cycle during operation by the second control program table.
According to the present invention, even in case of a
long-time power outage, data required for control is capable
of being stored on amemory. In addition, when chargeable backup
means is present, a large amount of control processing is
20 achievable by use of a feature of a volatile memory having a
higher access speed than that of a nonvolatile memory.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a blockdiagramshowing an internal configuration
25 of a control controller of this embodiment;
Fig. 2 shows an example of a c o n f i g u r a t i o n o f a c o n t r o l
program address t a b l e ;
Fig. 3 shows examples of c o n f i g u r a t i o n s o f a b a c k u p m e a n s
presence f l a g and a c o n t r o l program t a b l e ;
5 Fig. 4 is a flowchart showing a backup means presence
d e t e r m i n a t i o n ;
Fig. 5 is a t a b l e of d e t e r m i n a t i o n r e s u l t s by t h e flow
of Fig. 4;
Fig. 6 i s a f l o w c h a r t of c o n t r o l program a d d r e s s t a b l e
10 s t o r a g e ; and
Fig. 7 is a f l o w c h a r t of a c o n t r o l program t a b l e backup.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Acomputer system, which i s one embodiment o f t h e p r e s e n t
15 i n v e n t i o n , is e x p l a i n e d by use of a c o n t r o l c o n t r o l l e r a s its
one example i n r e f e r e n c e t o F i g s . 1 t o 6.
[EMBODIMENTS]
Fig. 1 i s a block diagram showing an i n t e r n a l c o n f i g u r a t i o n
of a c o n t r o l c o n t r o l l e r of t h i s embodiment.
2 0 A g e n e r a l c o n t r o l c o n t r o l l e r 1 i n c l u d e s a p r o c e s s i n g u n i t
2, a m e m o r y u n i t 3 , etc. T h e p r o c e s s i n g u n i t 2 p e r f o r m s v a r i o u s
o p e r a t i o n s i n r e f e r e n c e t o t h e memory u n i t 3, and p r o p e r l y
t r a n s m i t s a n d r e c e i v e s controlinformationtoandfromexternal
d e v i c e s .
2 5 A c o n t r o l power not shown is s u p p l i e d t o t h e c o n t r o l
c o n t r o l l e r 1. A d d i t i o n a l l y , backup means Bat chargeable a s
a backup i n case of f a i l u r e of c o n t r o l power may be connected
t o t h e c o n t r o l c o n t r o l l e r 1. The p r e s e n t i n v e n t i o n has a f e a t u r e
t h a t an a c t i o n i s p o s s i b l e a f t e r a power outage i r r e s p e c t i v e
5 of t h e presence of t h e chargeable backup means Bat.
T h e m e m o r y u n i t 3 i n c l u d e s a p l u r a l i t y o f t y p e s of s t o r a g e
means. As shown, a v o l a t i l e m e m o r y 4 t h a t r e w r i t e s a n d d e l e t e s
d a t a a t high speed but d e l e t e s d a t a when t h e power is down,
a n o n v o l a t i l e memory 6 t h a t r e w r i t e s and d e l e t e s d a t a a t low
10 speedbutstoresdataevenwhenthepoweris down, a flashmemory
5 t h a t i s r e w r i t a b l e and d e l e t e s no d a t a even when t h e power
is down, e t c . a r e used.
As t h e v o l a t i l e memory 4 , a SRAM ( S t a t i c Random Access
Memory), a DRAM (Dynamic Random Access Memory), e t c . a r e used.
15 As t h e n o n v o l a t i l e memory 6, a MRAM ( M a g n e t o r e s i s t i v e Random
AccessMemory) i s u s e d . T h e f l a s h m e m o r y 5 i s a k i n d o f E E P R O M s .
Next, t h e p r o c e s s i n g f u n c t i o n and s t o r a g e c o n t e n t i n t h e
memory4 of Fig. l a r e e x p l a i n e d . A t f i r s t , t h e s t o r a g e c o n t e n t
is h e l d i n t h e form of a d a t a b a s e o r a t a b l e ( h e r e i n a f t e r c a l l e d
20 j u s t a t a b l e TB) . When t h e c o n t e n t s t o r e d on t h e t a b l e TB roughly
includesdatasuchascontrolprograms, a d d r e s s e s o f t h e c o n t r o l
programs, o t h e r f l a g s , e t c .
The c o n t r o l programs a r e held on c o n t r o l program t a b l e s
TB1 and TB2 r e s p e c t i v e l y held on t h e n o n v o l a t i l e memory 6 and
25 v o l a t i l e m e m o r y 4 . Thecontentsofprogramsheldonthecontrol
program t a b l e T B l o f t h e n o n v o l a t i l e memory 6 having low speed
but l a r g e c a p a c i t y a r e s u b s t a n t i a l l y t h e same a s t h o s e of
programs held on t h e c o n t r o l program t a b l e TB2 of t h e v o l a t i l e
memory 4 having high speed b u t s m a l l c a p a c i t y .
5 In a s s o c i a t i o n with a d d r e s s e s of t h e c o n t r o l programs,
c o n t r o l program address t a b l e s TBlA and TB2A t h a t manage
addresses of programs used f o r o p e r a t i o n s i n t h e c o n t r o l l e r
1 a r e provided i n t h e v o l a t i l e memory 4 . The c o n t r o l program
a d d r e s s t a b l e T B l A m o n i t o r s a n d s t o r e s a d d r e s s e s o f t h e c o n t r o l
10 program t a b l e TB1. The c o n t r o l program address t a b l e TB2A
monitors a n d s t o r e s a d d r e s s e s o f t h e c o n t r o l p r o g r a m t a b l e T B 2 .
In a s s o c i a t i o n with a d d r e s s e s o f t h e c o n t r o l programs,
a t h i r d c o n t r o l program address t a b l e TB3A is provided i n t h e
v o l a t i l e m e m o r y 4 . The s t o r a g e c o n t e n t o f t h e c o n t r o l program
15 address t a b l e TBlA and t h e s t o r a g e c o n t e n t of t h e c o n t r o l program
address t a b l e TB2A a r e each s t o r e d i n e i t h e r a primary a r e a
o r secondary a r e a of t h e c o n t r o l program address t a b l e TB3A.
The v o l a t i l e memory 4 i n c l u d e s a backup means presence
f l a g t a b l e TB4 a s a r e g i o n t o s t o r e a f l a g showing t h e presence
20 of t h e backup means.
Next, t h e p r o c e s s i n g f u n c t i o n s i n t h e memory 4 of Fig.
1 a r e e x p l a i n e d . By use of t h e above s t o r a g e c o n t e n t h e l d i n
t h e memory u n i t 3, t h e following p r o c e s s i n g f u n c t i o n s a r e
executedbyamemorycontroldevicenotshown. These f u n c t i o n s
25 a r e shown and provided i n t h e v o l a t i l e memory 4 a s a c o n t r o l
program address t a b l e s t o r a g e f u n c t i o n PR1, a backup means
presence d e t e r m i n a t i o n f u n c t i o n PR2, a c o n t r o l program t a b l e
backup f u n c t i o n PR3, and a c o n t r o l programprocessing f u n c t i o n
PR4.
5 The c o n t r o l program address t a b l e s t o r a g e f u n c t i o n PR1,
which i s t h e f i r s t of t h e p r o c e s s i n g f u n c t i o n s , r e f e r e n c e s t h e
backup means presence f l a g t a b l e TB4 t o give f i r s t p r i o r i t y
(primary) t o anyone of t h e s t o r a g e c o n t e n t of t h e c o n t r o l program
a d d r e s s t a b l e T B 2 A a n d t h a t o f t h e c o n t r o l p r o g r a m a d d r e s s t a b l e
10 TBlA and second p r i o r i t y (secondary) t o t h e o t h e r and then t o
s t o r e them on t h e c o n t r o l program address t a b l e TB3A.
Next, t h e backup means presence d e t e r m i n a t i o n f u n c t i o n
PR2performsprocessinginreferencetothebackupmeanspresence
f l a g t a b l e TB4, c o n t r o l program t a b l e TB2, and c o n t r o l program
15 t a b l e TB1.
T h e c o n t r o l p r o g r a m t a b l e b a c k u p f u n c t i o n P R 3 s t o r e s d a t a
o f t h e c o n t r o l p r o g r a m t a b l e TB2 onto t h e c o n t r o l p r o g r a m t a b l e
TB1 i n r e f e r e n c e t o t h e backup means presence f l a g t a b l e TB4.
The c o n t r o l program p r o c e s s i n g f u n c t i o n PR4 r e f e r e n c e s
20 t h e c o n t r o l program address t a b l e TB3A d e s c r i b i n g a d d r e s s e s
of t h e c o n t r o l program t a b l e TB2 o r c o n t r o l program t a b l e TB1,
and performs p r o c e s s i n g i n r e f e r e n c e t o e i t h e r t h e c o n t r o l
program t a b l e TB2 o r c o n t r o l program t a b l e TB1.
I n r e f e r e n c e t o t h e drawings, t h e p r o c e s s i n g f u n c t i o n s
25 and s t o r a g e c o n t e n t i n t h e memory 4 a r e e x p l a i n e d below i n d e t a i l .
The storage content is first explained using Fig. 2 and Fig.
3. Fig. 2 showsanexampleofaspecificconfiguration (storage
contentandinterrelation) ofthecontrolprogramaddresstables
TBlA, TB2A, and TB3A in the configuration of Fig. 1.
5 In Fig. 2, two tables, a primary table TB3AP and a secondary
table TB3AS, are provided in the control program address table
TB3A. The primary table TB3AP has n number of table starting
addressesfromatable-lstartingaddress6Oatotable-nstarting
address 60nto store control programaddress information. The
10 secondarytable TB3AS has n number oftable starting addresses
froma table-2 starting address 61a to a table-n starting address
61n to store control program address information.
On the other hand, the control programaddress table TB2A
has table starting addresses from a volatile-memory table-1
15 starting address 70a to a volatile-memory table-n starting
address 70nto store control programaddress information. The
c o n t r o l p r o g r a m a d d r e s s t a b l e T B l A h a s t a b l e s t a r t i n g a d d r e s s e s
from a nonvolatile-memory table-1 starting address 71a to a
nonvolatile-memory table-n starting address 71n to store
20 control program address information.
Either the control program address information held on
the control program address table TB2A or the control program
address information held on the control program address table
TBlAis s t o r e d o n t h e p r i m a r y t a b l e T B 3 A P a n d t h e o t h e r i s stored
25 onthe secondarytableTB3AS. It is determinedwhetherto store
t h e one o r t h e o t h e r on t h e primary t a b l e TB3AP i n accordance
w i t h t h e storagecontentofthebackupmeanspresence f l a g t a b l e
TB4, a s mentioned l a t e r .
The p r o c e s s i n g u n i t 2 performs o p e r a t i o n s i n r e f e r e n c e
5 t o t h e c o n t r o l programaddresses describedontheprimarytable
TB3AP. The c o n t r o l program a d d r e s s e s d e s c r i b e d on t h e
secondary t a b l e TB3AS a r e waited f o r and used i n backups.
Next, Fig. 3 shows s t o r a g e c o n t e n t s of t h e backup means
presence f l a g t a b l e TB4, c o n t r o l p r o g r a m t a b l e TB2, a n d c o n t r o l
10 program t a b l e TB1 i n t h e c o n f i g u r a t i o n o f F i g . 1.
The backup means presence f l a g t a b l e TB4 of Fig. 3 i n c l u d e s
a backup means presence 100 and primary information 101. In
t h i s embodiment, whenthedataheldinthebackupmeanspresence
100 is "0," t h e c h a r g e a b l e backup means Bat is not connected
15 t o t h e c o n t r o l c o n t r o l l e r 1, and when t h e d a t a is "1," t h e
chargeable backup means Bat is connected t o t h e c o n t r o l
c o n t r o l l e r 1. The s t a t e where t h e c h a r g e a b l e backupmeans Bat
is ( n o t ) connected d o e s not s o l e l y r e f e r t o t h e presence of
mechanical connection. The s t a t e where t h e chargeable backup
20 means Bat having an i n s u f f i c i e n t charge c a p a c i t y is connected
maybe e q u i v a l e n t t o no connection. The l a t e s t connection s t a t e
o f t h e c h a r g e a b l e backupmeans Bat is always h e l d i n t h e backup
means presence 100.
When t h e d a t a held i n t h e primary information 101 is "0,"
25 t h e v o l a t i l e memory 4 is t h e primary memory TB3AP. When t h e
data is "1," the nonvolatile memory 6 is the primary memory
TB3AP.
On the other hand, in association with the control program
tables TB1 and TB2 of Fig. 3, the control program table TB2
5 has a backup cycle TB3AO and n number of data tables from a
control program table la (TB3Ala) to a control program table
na (TB3Aln). The control program table TB1, as well as the
control program table TB2, has at least a backup cycle 120 and
n number of data tables from a control program table lb (121a)
10 to a control program table nb (121n).
As described above, the storage content in the memory
4 has been explained using Figs. 2 and 3. Next, in reference
to Figs. 4, 6, and 7, the processing functions in the memory
4 are explained in detail. First, Fig. 4 shows the processing
15 flow of the backup means presence determination function PR2
shown in Fig. 1.
At processing step S150, which is the first processing
of Fig. 4, it is determined whether the backup means presence
determination function PR2 is a first operation after power-up
20 of the control controller 1. When the backup means presence
determination function PR2 has been already operated, the
processingends. Whenthebackupmeanspresencedetermination
function PR2 is the first operation, the flow proceeds to
processing step S151.
2 5 At processing step S151, in reference to the primary
i n f o r m a t i o n 1 0 1 i n t h e b a c k u p m e a n s p r e s e n c e d e t e r m i n a t i o n f l a g
table TB4 of Fig. 3, determination is made subject to the
referenced information. The backup means presence
determination flag table TB4 describes that, when the primary
5 information 101 is "0," the volatile memory 4 is the primary
memory TB3AP, and when the primary information 101 is "1," the
nonvolatile memory 6 is the primary memory TB3AP. As a result
ofthe determination at processing step S151, when the primary
information 101 is "0," the flow proceeds to processing step
10 S154. When theprimaryinformation 101 is "1," the flowproceeds
to processing step S152.
At processing steps152 next to the process when theprimary
information 101 is "1" and the state where "the nonvolatile
memory 6 is the primary memory TB3AP" is indicated, the backup
15 means presence 100 in the backup means presence determination
flag table TB4 of Fig. 3 is referenced, and the determination
ismade subject tothe reference. In thebackupmeans presence
100, the state where the chargeable backupmeans is not connected
to the control controller 1 is stored as "0," and the state
20 where the chargeable backup means is connected to the control
controller 1 is stored as "1." In this determination, when
the backup means presence 100 is "0," the flow proceeds to
processing step S153. When the backup means presence 100 is
"1," the flow proceeds to processing step S154.
2 5 AtprocessingstepS153, dataofthecontrolprogramtable
TB1 is transferred to the control program table TB2, and the
flow proceeds to processing step S154. At processing step S154,
the backup means presence 100 is rewritten to "1," and the
processing ends.
5 Fig. 5 shows atable of determination results ofthe flow
of Fig. 4. In this figure, determinations of processing steps
S150 to S154 are shown in the longitudinal direction, and the
determination results are shown in the lateral direction. As
will be seen from the table of the results, the processing at
10 the first activation is shown in the processing of fig. 4, and
the processing at the second or subsequent time is not a target
of this processing.
I n c a s e o f t h e f i r s t p r o c e s s i n g , t h e b a c k u p m e a n s p r e s e n c e
100 is finally set to "1," but division into some cases is
15 performed in the procedure up to this final setting. When the
primary information 101 is "0," the backup means presence 100
is set to "1" directly. Since this case is in the mode of
operating in reference to the control program table TB1 in the
nonvolatile memory 6, the control programs are saved without
20 damageirrespectiveofapoweroutage. Accordingly, thebackup
means may be set as present.
When the primary information 101 is "1" and the backup
means presence 100 is "1," the backup means presence 100 is
set to "1." This case is in the mode of operating in reference
25 to the control program table TB2 in the volatile memory 4. Since
thebackupmeans Bat is actuallyconnected, this case signifies
just a reconfirmation of the connection of the backup means
Bat.
The case where the primary information 101 is "1" and
5 the backup means presence 100 is "0" is in the mode of operating
in reference to the control program table TB2 in the volatile
memory 4. Data in the control program table TB2 may be lost
during power down because of no connection of the backup means
Bat. Therefore, after the content ofthe control programtable
10 TB1 in the nonvolatile memory 6 is transferred to the control
program table TB2 in the volatile memory 4, the backup means
is set as present.
Next, the specific content of processing of the control
program address table storage function PR1 shown in Fig. 1 is
15 explained. Fig. 6 shows a processing flow in the control program
address table storage function PR1. Here, in accordance with
t h e p r i m a r y i n f o r m a t i o n 1 0 1 , thecontrolprogramaddress tables
TBlAand TB2Ato be storedinthe primary and secondary regions
in the control program address table TB3A are determined.
20 At the first processing step S200, after the control
controller1ispoweredon, it is determinedwhether thecontrol
program address table storage function PR1 is performed for
the first time. When the processing of the control program
address table storage function PRlis the second or subsequent
25 processing after the function has been already performed, the
processing ends.
When the control program address table storage function
PR1 is performed for the first time, the flow proceeds to
processing step S201. At processing step S201, determination
5 is made subject tothe primary information 101of Fig. 3. When
the primary information 101 is "1" (the volatile memory 4 is
set as the primarymemory TB3AP) , the flow proceeds to processing
step S202. When the primary information 101 is "0" (the
nonvolatile memory 6 is set as the primary memory TB3AP), the
10 flow proceeds to processing step S204.
At processing step S202 in which the volatile memory 4
is set as the primary memory TB3AP, the information from the
volatile-memory table-1 starting address 70a to
volatile-memorytable-n starting addresses 70n ofthe control
15 program address table TB2A is stored on the regions from the
table-1 starting address 60a to table-n starting address 60n
of the primary table TB3AP of Fig. 2. Then, the flow proceeds
to processing step S203.
Then, at processing step S203, the table starting
20 addresses fromthenonvolatile-memorytable-lstartingaddress
71a to nonvolatile-memorytable-n starting address 71n of the
control program address table TBlA are stored on the regions
fromthetable-lstartingaddress61atotable-nstartingaddress
61n of the secondary table TB3AS, and the processing ends.
2 5 At processing step S204 in which the nonvolatile memory
6 is set as theprimarymemoryTB3AP, the table startingaddresses
from the nonvolatile-memory table-1 starting address 71a to
nonvolatile-memorytable-n starting address 71n ofthe control
program address table TBlA are stored on the regions from the
5 table-1 starting address 60a to table-n starting address 60n
of the primary table TB3AP. Then, the flow proceeds to
processing step S205.
At processing step S205, the table starting addresses
from the nonvolatile-memory table-1 starting address 71a to
10 nonvolatile-memorytable-n starting address 71n ofthe control
program address table TBlA on the regions from the table-1
starting address 61a to table-n starting address 61n of the
secondary table TB3AS. Then, the processing ends.
Through the processing of the flows of Fig. 4 and Fig.
15 5 described above, at the first activation, the subsequent
control program tables and the corresponding control program
address table are selected.
When the chargeable backup means Bat is present, the
control programprocessing function PR4 is performedusingthe
20 control program table TB2 mapped in the volatile memory 4. Here,
even in case of a short power interruption in the control
controller 1, the data stored on the control program table TB2
bythechargeablebackupmeansremainsstored. Therefore, even
after power is provided again, the control program processing
25 functionPR4 canreferencethedataofthecontrolprogramtable
TB2 just before the short power interruption. Accordingly,
processing is performable on the volatile memory 4.
On the other hand, when the chargeable backup means Bat
is absent, the control program processing function PR4 is
5 performed using the control program table TB1 mapped in the
nonvolatile memory 6. Here, even in case of a short power
interruption in the control controller 1, the control program
table TB1 can store the data just before the short power
interruption by use of the characteristic of the nonvolatile
10 memory 6 on which data is storable without power. Therefore,
even after power is provided again, the control program
processing function PR4 can reference the data of the control
program table TB1 just before the short power interruption,
and processing is performable on the nonvolatile memory 6.
15 Next, the specific content of processing in the control
program table backup function PR3 shown in Fig. 1 is explained
using Fig. 7. Fig. 7 is a flowchart showing the specific content
ofthe processingin the control programtable backup function
PR3. Here, data of the control program table TB2 is stored
20 in the control program table TB1 in reference to the backup
means presence flag TB4.
At the first processing step S250 in Fig. 7 showing the
processing flow in the control program table backup function
PR3, determination is made subject to the primary information
25 101. The processing ends when the primary information 101 is
"0. " When the primary information 101 is "1, " the flow proceeds
to processing step S251.
At processing step S251, the flowproceedsto processing
step S252 in reference to a backup cycle T and a control cycle
5 t contained in the control controller 1. At processing step
S252, the backup cycle T is compared to the control cycle t
contained in the control controller 1, and it is determined
whether a backup is to be performed at the cycle. As a result,
when the backup is to be performed at the control cycle T, the
10 flow proceeds to processing step S253. When the backup is not
to be performed at the control cycle T, the flow proceeds to
processing step S252 again at the next control cycle.
At processing step S253, control program tables from a
control program table lla to a control program table lln of
15 the control program table TB2 are stored on the regions from
the control program table 121a to the control program table
121n of the control program table TB1 shown in Fig. 3, and the
processing ends. This data transfer is shown by the dotted
lines in Fig. 3.
2 0 Through this processing, evenwhen the chargeable backup
means is lostduringthe storage ofthe control programaddress
table TB2A onto the primary table TB3APr the control program
processing function PR4 can be restarted by using the data at
the cycle at which the backup has been performed by combining
25 this processing with the backup means presence determination
function PR2 showninFig. 4 andthenbytransferringthecontrol
programtableTB1, backedupcyclically, tothe control program
table TB2 after power is down and up again.
Finally, in reference to the control programaddress table
5 TB3A describing addresses of the control program table TB2 or
control program table TB1 and to either the control program
table TB2 or control program table TB1, the control program
processing function PR4 is performed.
Through the above processing, in the control controller
10 of the present invention, the address tables describing the
addresses of the program tables used by the control programs
are stored after two definitions of placements of the tables
on the volatile memory and on the nonvolatile memory. In
addition, by providing the presence information about the
15 chargeable backup means, either of the address tables is
determined to start execution of the control programs.
Afterthat, whenthechargeablebackupmeansis connected
to the control controller, the volatilememory is set as primary,
the nonvolatile memory is set as secondary, and the primary
20 data is transferred at a fixed cycle. When the power of the
control controller is down for long time, the data is transferred
from the secondary to the primary.
When the chargeable backup means is not connected to the
control controller, the nonvolatile memory is set as primary,
25 and the control programs are executed only by the primary.
Reference Signs List
l...Control Controller
2...Processing unit
5 3...Memory unit
4...Volatile memory
5...Flash memory
6...Nonvolatile memory
PR1 . . . Control program address table storage function
10 PR2 . . . Backup means presence determination function
PR3 . . . Control program table backup function
PR4 . . . Control program processing function
TBlA, TB2A, TB3A ... Control program address table
TB4 . . . Backup means presence flag table
15 TB1, TB2 . . . Control program table
TB3AP ... Primary table
TB3AS . . . Secondary table
6Oa . . . Table-1 starting address
60b . . . Table-2 Starting address
20 6On . . . Table-n starting address
6la . . . Table-1 starting address
6lb . . . Table-2 Starting address
6ln . . . Table-n starting address
70a . . . Volatile-memory table-1 starting address
25 70b . . . Volatile-memory table-2 starting address
70n . . . Volatile-memory table-n starting address
71a . . . Nonvolatile-memory table-1 starting address
71b . . . Nonvolatile-memory table-2 starting address
71n . . . Nonvolatile-memory table-n starting address
5 100 . . . Backup means presence
101 . . . Primary information
110, 120 . . . Backup cycle
llla . . . Control program table la
lllb . . . Control program table 2a
10 llln . . . Control program table na
12la ... Control program table lb
l2lb . . . Control program table 2b
12ln . . . Control program table nb
WHAT IS CLAIMED IS:
1. A computer system comprising a memory unit having
a nonvolatile memory and a volatile memory and a processing
5 unit to execute control programs described on control program
tables of the memory unit by use of the processing unit,
the nonvolatilememoryincludinga first control program
tableandthevolatilememoryincludingasecondcontrolprogram
table,
the volatile memory including:
a first control program address table that defines
addresses ofthe first control programtable in the nonvolatile
memory;
a second control program address table that defines
15 addresses of the second control program table in the volatile
memory;
a third control program address table that defines
addresses referenced by the control programs executed in the
processing unit; and
a backup means presence flag table that shows presence
of backup means chargeable upon power down,
whereina control programaddress table storage function
includes processing to select and store on the third control
program address table the first control program address table
25 and the second control program address table in reference to
the backup means presence flag table, a backup means presence
determination function includes processing to reference the
backup means presence flag table when the computer system is
activated and to transfer content ofthe first control program
5 table to the second control program table, a control program
tablebackupfunctionincludesprocessingtotransferthesecond
control program table to the first control program table
periodically with reference tothe backup means presence flag
table, and the control program processing function includes
10 processing to perform operations in reference to the control
program table.
2. The computer system according to claim 1, wherein
the backup means presence flag table has backup means presence
15 informationandprimaryinformation, thebackupmeanspresence
information shows presence of connection of the chargeable
backup means, and the primary information shows information
about whether to select the first control program table or the
secondcontrolprogramtableinthethirdcontrolprogramaddress
20 table when the control programs are executedinthe processing
unit.
3. The computer system according to claim 1, wherein
the first and second control program tables have each a backup
25 cycle and control-program dedicated tables, the backup cycle
shows a backup c y c l e f o r a c y c l i c a l t r a n s f e r using t h e c o n t r o l
program t a b l e backup f u n c t i o n , t h e control-program d e d i c a t e d
t a b l e s show t a b l e s used i n t h e c o n t r o l program p r o c e s s i n g
f u n c t i o n , and t h e c o n t r o l program p r o c e s s i n g f u n c t i o n
5 r e f e r e n c e s t h e c o n t r o l program address t a b l e t o a c q u i r e each
t a b l e a d d r e s s , t h e each t a b l e address being then capable of
being r e f e r e n c e d .
4. A computer system according t o claim 1, i n which t h e
10 c o n t r o l program address t a b l e i n c l u d i n g :
a primary t a b l e ; and
a secondary t a b l e ,
wherein t h e primary t a b l e shows an address t a b l e
r e f e r e n c e d b y t h e c o n t r o l programprocessing f u n c t i o n , and t h e
15 secondary t a b l e shows an address t a b l e r e f e r e n c e d by t h e c o n t r o l
program t a b l e backup f u n c t i o n .
5. A computer system comprising a memory u n i t having
a n o n v o l a t i l e memory and a v o l a t i l e memory and a p r o c e s s i n g
20 u n i t t o execute c o n t r o l programs d e s c r i b e d on c o n t r o l program
t a b l e s of t h e memory u n i t by use of t h e p r o c e s s i n g u n i t ,
wherein t h e n o n v o l a t i l e memory i n c l u d e s a f i r s t c o n t r o l
p r o g r a m t a b l e andthevolatilememoryincludes a s e c o n d c o n t r o l
p r o g r a m t a b l e , it i s d e t e r m i n e d w h e t h e r chargeablebackupmeans
25 i s p r e s e n t a n d w h e t h e r t h e f i r s t o r s e c o n d c o n t r o l p r o g r a m t a b l e
is used. preferentially upon power up, content of the first
control program table is transferred to the second control
program table when there is no connection of the chargeable
backup means and the second control program table is used, and
5 content of the second control program table is transferred to
the first control program table at each predetermined control
cycle during operation by the second control program table.