4-168 Series 90-30/20/Micro Programmable Controllers Reference Manual – September 1998 GFK-0467K
4
Read/Write Data (Function #3)

The read/write function reads a word of extra status data from a module specified in the parameter

block, then writes a data value between 0 and 15 from the parameter block to that module. This

read write process is repeated for each module in a list in the parameter block. The parameter block

(N * 3) + 3 words of reference memory, where N is the number of modules with which data will be

exchanged.

Location Field Meaning
Address Function 3 = read/write
Address + 1 Error Code An error code is placed here if the function fails because
any of the modules is not present, inappropriate, or not
working. No error code is set if the function executes but
any of the modules does not receive the write data
properly
Address + 2 First rack & slot Rack and slot number (in the form RRSS in hexadecimal,
where RR is the rack number and SS is the slot number)
of the first module with which data will be exchanged
Address + 3 Read data from
first module The data read from the first module will be placed here
Address + 4 Write data for
first module This data value will be written to the first module
Address + 5 Second rack &
slot Rack and slot number (in the form RRSS in hexadecimal,
where RR is the rack number and SS is the slot number)
of the second module with which data will be exchanged
Address + 6 Read data from
second module The data read from the second module will be placed here
Address + 7 Write data for
second module This data value will be written to the second module
Address + ((I-1) * 3) + 2 Ith rack & slot Rack and slot number (in the form RRSS in hexadecimal,
where RR is the rack number and SS is the slot number)
of the Ith module with which data will be exchanged
Address + ((I-1) * 3) + 3 Read data from
Ith module The data read from the Ith module will be placed here
Address + ((I-1) * 3) + 4 Write data for
Ith module This data value will be written to the Ith module
Address + ((N-1) * 3) + 2 Last rack & slot Rack and slot number (in the form RRSS in hexadecimal,
where RR is the rack number and SS is the slot number)
of the last module with which data will be exchanged
Address + ((N-1) * 3) + 3 Read data from
last module The data read from the last module will be placed here
Address + ((N-1) * 3) + 4 Write data for
last module This data value will be written to the last module
Address + (N * 3) + 2 End of list
indicator A zero in this word indicates the end of the list of modules