Cutler-Hammer D50 - Read Bits and Words

Appendix A: D50 PLC Communication Protocol 165
Read Bits and Words
• Reads the bits and/or word contents of the specified absolute addresses.
• Can read bits and words regardless of their order and location in memory.
Query (Q) Frame
Response (R) Frame
Methods of assigning bit/word abs. address
0 0 Bit Address
0 1 Word Address
1 x Not Used
A
x = A0, A1,…, An Dx = D0, D1,…, Dn
A
ssigning absolute address for bits
A
bs. address for the K12 12th bit = $14CC
A
x = 0001 0100 1100 1100
A
x L = $CC, H = $14
A
ssigning absolute address for word
A
bs. address for the K12 word = $014C
A
x = 0100 0001 0100 1100
A
x L = $4C, H = $41
Absolute Address
15
14
13
0
DASA $05 L L H L H … L H L H
A
OA1 AN CRC
DA SA $85 Lx DO L H … L H L H
For the A0, A1,…, An requested by the Q, the content D0, D1,…, Dn of
the word/bit is returned.
If Ax denotes a bit address, the Dx data is 1 byte (On = $FF, Off = $00),
and if Ax denotes a word address, the Dx data is 1 word (2 bytes).
The size and location of the
returned data depends on the
combination of bit/word
addresses requested. The Lx
parameter should be checked to
verify data size.
D1 Dn CRC
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