IDEC MicroSmart - Manual (Page 164)

5: S PECIAL F UNCTIONS
5-44 « FC4A M ICRO S MART U SER ’ S M ANUAL »
Data Movement of Preset Data Registers
Like preset values for timers and counters (page 7-13), the preset data of expansion data registers can be changed in the
RAM, the changed data can be cleared, and also stored to the EEPROM. The data movement is described below.
At Power-up and User Program Download
When the user program is downloaded to the CPU
module, the data of preset data registers are also
downloaded to the EEPROM. Each time the CPU is
powered up, the data of preset data registers are
loaded to the RAM. If the data of the expansion data
registers have been changed as a result of advanced
instructions or through communication, the changed
data is cleared and initialized with the data of the pre-
set data registers when the CPU is powered up again.
Since expansion data registers D2000 through D7999 are all “keep” types, the data in ordinary data registers are retained
when the CPU is powered down.
Initializing Relay
When the internal relay designated as an initializing relay is turned on,
the data of preset data registers are loaded to the RAM as is the case
when the CPU is powered up.
When the initialization is complete, the initializing relay is turned off
automatically. When a user program is used to turn on the initializing
relay, use a SOTU or SOTD to make sure that the initializing relay
turns on for one scan only. When an initializing relay is not designated,
the initialization cannot be performed.
Backup Relay
When the internal relay designated as a backup relay is turned on, the
data of preset data registers are written from the RAM to the EEPROM
as is the case with confirming changed timer/counter preset values.
When the CPU is powered up again, the new data is loaded from the
EEPROM to the RAM. When the user program is uploaded to
WindLDR , the new data is also uploaded to the expansion data registers.
When the backup is complete, the backup relay is turned off automati-
cally. When a user program is used to turn on the backup relay, use a SOTU or SOTD to make sure that the backup relay
turns on for one scan only. When a backup relay is not designated, the backup cannot be performed.
Special Internal Relays for Expansion Data Registers
While data write from the RAM to expansion data register preset range 1 or 2 in the EEPROM is in progress, special inter-
nal relay M8026 or M8027 turns on, respectively. When data write is complete, the special internal relay turns off.
Notes for Using Expansion Data Registers:
•
All expansion data registers are “keep” types and cannot be designated as “clear” types using the Function Area Settings.
•
When expansion data registers are designated as source or destination operands of advanced instructions, the execution
time takes slightly longer compared with ordinar y data registers D0 through D1299.
•
When a user program RAM sum check error has occurred, the data of preset expansion data registers are loaded to the
RAM as is the case when the CPU is powered up.
•
When the initializing relay is turned on, the scan time is extended until the data load from the EEPROM is completed by
approximately 7 ms for ever y 1000 words of data read from the EEPROM. The data size can be calculated from the follow-
ing formula:
Data size (words) = 8.5 + Quantity of preset data registers
•
When the backup relay is turned on, the scan time is extended until the data write to the EEPROM is completed for several
scans by approximately 200 ms in ever y scan.
•
Writing to the EEPROM can be repeated a maximum of 100,000 times. Keep writing to the EEPROM to a minimum.
WindLDR MicroSmart CPU Module
Download
User Program
EEPROM
RAM User Program
Preset
Values
MicroSmart CPU Module
Initialize
User Program
EEPROM
RAM
Preset
Values
MicroSmart CPU Module
Backup
User Program
EEPROM
RAM
Changed
Values