1 - 30 Modular LYNX System 12.05.2003
Read/Write an I/O Group
When using the IO variable to read the state of a group of
inputs/outputs, or write to a group of outputs you would first
want to configure the entire I/O group to be general purpose
inputs or outputs using the IOS variable. In this case the
response or input won’t be a logic state of 1 or 0, but rather the
decimal equivalent (0 to 63) of the 6 bit binary number repre-
sented by the entire group.
When addressing the I/O as a group the LSB (Least Significant
Bit) will be line 1 of the group, (e.g. 21, 31, 41, 51). The MSB
(Most Significant Bit) will be line 6 of the group (e.g. 26, 36, 46,
56).
The table on the left shows the bit weight of each I/O line in the
group. It also illustrates the state should 6 LED’s be connected
to I/O group 20 when entering the IO variables in this exercise.
Configure the IOS variable such that group 20 is all general
purpose outputs, active low or:
IOS 20 = 0,1,0
Enter the following in the terminal:
IO 20 = 35
As shown in the table I/O lines 26, 22 and 21 should be illumi-
nated, 25, 24 and 23 should be off.
Enter this next:
IO 20 = 7
Now I/O 21, 22 and 23 should be illuminated.
IO 20 = 49
I/O 26, 25, and 21 are illuminated.
111
000
BINARY STATE OF I/O GROUP 20
IO 20 = 35
I/O 21
LSB
I/O 26
MSB
I/O 22I/O 23I/O 24I/O 25
32
21
16 8
4
BIT WEIGHT DISTRIBUTION TABLE
FOR GROUP 20 I/O
I/O 21
LSB
I/O 26
MSB
I/O 22I/O 23I/O 24I/O 25
011
001
BINARY STATE OF I/O GROUP 20
IO 20 = 7
I/O 21
LSB
I/O 26
MSB
I/O 22I/O 23I/O 24I/O 25
101
100
BINARY STATE OF I/O GROUP 20
IO 20 = 49
I/O 21
LSB
I/O 26
MSB
I/O 22I/O 23I/O 24I/O 25
NOTE: You can only write to General Purpose Outputs. If you
attempt to write to and input or dedicated output type an error
will occur!
N
Table 6.4: Binary State of Outputs
