
3–6 Communicating with FLEX I/O Modules
Publication 1794ĆUM009D-EN-P - April 2004
Use standard addressing when:
• you need full FLEX I/O module functionality, such as delay time
selection on input modules, fuse-blown indication on the
1794-OB8EP, etc.
• using combination modules, such as the 1794-IB10XOB6 10 in/6
out module
In standard mode, each module position equals one I/O group – 1
word of input image and 1 word of output image. If 32-pt input or
output modules are used, only the lower 16 bits are available. All 32
bits of the 32–pt combination modules are available.
Any combination of digital or analog modules.
Eight terminal bases per adapter (maximum)
Adapter
20128
Each terminal base represents 1 I/O group
Input Output Input Output Analog Analog Output Input
Standard Addressing
00071017 00071017
0
1
2
3
4
5
6
7
I/O Group
Input Image Table Output Image Table
M0 M1 M2 M3 M4 M5 M6 M7
IL = Input Low Byte
IH = Input High Byte
OL = Output Low Byte
OH = Output High Byte
MCB = Module Control Byte (output data)
MSB = Module Status Byte (input data)
ASB/E
IH IL IH IL
OH OL
IB16 IB16IB16
OH OL
M0ĆIL
M1ĆIL
M4ĆMSB
M0ĆIH
M1ĆIH
M0ĆOL
M1ĆOL
M4ĆMCB
M0ĆOH
M1ĆOH
MCB
MSB
OB16
MCB
MSB
IE8 IE8
OH OL
IH IL
OB16OB16
Standard Addressing Example
I/O Group 0 I/O Group 1 I/O Group 2 I/O Group 3
- 8 modules = 1 logical rack = 8 I/O groups
I/O Group 4 I/O Group 5 I/O Group 6 I/O Group 7
M5ĆMSB
M7ĆILM7ĆIH
M5ĆMCB
M6ĆOL
M7ĆOL
M6ĆOH
M7ĆOH
M2ĆILM2ĆIH M2ĆOLM2ĆOH
M3ĆOLM3ĆOH
M3ĆILM3ĆIH
M6ĆILM6ĆIH
1 module position is an I/O group
Legal Module Placement in Standard Addressing
Any module in any slot
OH OL OH OL OH OL
IH IL IH IL IH IL
Standard Addressing
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