Rockwell Automation 1775-S5_SR5,D17756.5.5 User Manual PLC-3 FAMILY I/0 - Manual (Page 146)

Binary Command Language
Appendix A
A-18
Read Block Command
Hex: 1F
Parameters: Starting address, size (in words) of the block
Description: The read block command reads a block of information
starting at a specific address. If you specify 0 for the size, the processor
returns the data from the address specified to the end of the section if this
does not include more than 63 words, or 63 words starting with the address
specified if the section is larger. The following example command block
reads the first two words of the input section:
STX
02
ISC
01
SIZ
08
CMD
1F 3C 02 00
ETX
03
CHK
6D
DAT
00 00 02 00
The data bytes store:
address mask (3C hex)
address byte specifying section 2 (input) (02 hex)
address byte specifying file 0 (00 hex)
address byte specifying structure 0 (00 hex)
address byte specifying word 0 (00 hex)
lower byte of size word (02 hex)
upper byte of size word (00 hex)
Notice that the size is specified in a word (two bytes). This is true of all
size specifiers within the data buffer of a command block.
The processor responds to a read block command with one of the
following response codes:
Response Codes
Hex Description
00 Success
01 Size too big
04 Address unknown
05 Address invalid - end of section
06 Access not allowed
08 Address not complete
If a success, size too big, or address invalid – end of section code
returns, the next byte contains the number of data words returned. The
data follows this byte.