Starting Your Processor
Chapter 5
5-5
In Figure 5.3, reading from left to right, the:
first number denotes the type of module:
- 0 output
- 1 input
second number denotes the I/O rack:
- In 2-slot addressing, the rack number is always 1.
- In 1-slot addressing, the rack number is either 1 or 2.
- In 1/2-slot addressing the rack number may be 1, 2, 3, or 4.
third number denotes an I/O group (0 to 7).
fourth and fifth numbers denote a terminal:
- In 2-slot addressing, 00 through 07 for the left slot of the I/O group,
10 through 17 for the right slot of the I/O group.
- In 1-slot addressing, 00 through 17 for each I/O group (slot).
- In 1/2-slot addressing, 00 through 17 for the upper half of each I/O
module (one group) and 00 through 17 for the lower half of each
module (another group).
2Slot Addressing
The processor addresses two I/O module slots as one I/O group.
Each physical 2-slot I/O group is represented by a word in the input image
table and a word in the output image table. Each input terminal
corresponds to a bit in the input image table word and each output terminal
corresponds to a bit in the output image table word.
The maximum number of bits available for one 2-slot I/O group is 32: 16
bits in the input image table word and 16 bits in the output image table
word. The type of discrete I/O module you install, either 8-point (standard
density) or 16-point (high-density, used in complementary mode)
determines the number of bits in the words that are used.
You select 2-slot addressing by setting switches 4 and 5 of the I/O chassis
backplane switch assembly:
Switch 4 to the OFF position
Switch 5 to the OFF position
