Table of Contents
Advertisement
Chapter 6. Service Request Function
6.24 SVC_REQ 23: Read Master Checksum
Use SVC_REQ 23 to read master checksums for the set of user program(s) and the configuration, and
to read the checksum for the block from which the service request is made.
There is no input parameter block for this service request. The output parameter block requires 15
words of memory.
Output
When a RUN Mode Store is active, the program checksums may not be valid until the store is
complete. To determine when checksums are valid, three flags (one each for Program Block
Checksum, Master Program Checksum, and Master Configuration Checksum) are provided at the
beginning of the output parameter block.
Address
Description
Address
Program Checksum Valid (0 = not valid, 1 = valid)
Address + 1
Master Program Checksum Valid (0 = not valid, 1 = valid)
Address + 2
Master Configuration Checksum Valid (0 = not valid, 1 = valid)
Address + 3
Number of LD/SFC Blocks (including _MAIN)
Address + 4
Size of User Program in Bytes (DWORD data type)
Address + 6
Program Set Additive Checksum
Address + 7
Program CRC Checksum (DWORD data type)
Address + 9
Size of Configuration Data in Kbytes
Address + 10 Configuration Additive Checksum
Address + 11 Configuration CRC Checksum (DWORD data type)
high byte: always zero
Address + 13
low byte: Currently Executing Block's Additive Checksum
Address + 14 Currently Executing Block's CRC Checksum
SVC_REQ 23 Example
When the timer using registers %P00013
through %P00015 expires, the checksum
read is performed. The checksum data
returns in registers %P00016 through
%P00030. The master program checksum
in registers %P00022 and %P00023 (the
program checksum is a DWORD data type
and occupies two adjacent registers) is
compared with the last saved master
program checksum. If these are different,
coil %M00055 is latched on. The current
master program checksum is then saved in
registers %P00031 and %P00032.
322
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
GFK-2950C
Advertisement
Table of Contents
