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Basic I/O Unit Instructions Section 3-22
Timing Chart
Flags
Precautions Do not read or write the system word (C2) from any other instruction.
DSW(210) will not operate correctly if the system word is accessed by another
instruction. The system word is not initialized by DSW(210) in the first cycle
when program execution starts. If DSW(210) is being used from the first cycle,
clear the system word from the program.
DSW(210) will not operate correctly if I/O refreshing is not performed with the
Input Unit and Output Unit connected to the digital switch or thumbwheel
switch after DSW(210) is executed. Consequently, do not connect the digital
switch or thumbwheel switch to the following Units.
• Communications Slaves (DeviceNet or CompoBus/S Slaves)
Example In this example, DSW(210) is used to read an 8-digit number from a digital
switch and outputs the resulting value constantly to D0 to D3. The digital
switch is connected through CIO 3 and CIO 104.
Since 8 digits of data are being read, C1 (D32000 in this case) is set to 0001
hex. D32001 is used as the system word.
00
01
02
03
04
05
O
10
0
10
1
10
2
10
3
D+1 D
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
I
Leftmost
4 digits
Rightmost
4 digits
Input data
CS signals
One Round Flag
RD (read) signal
16 cycles to complete one round of execution
Eight digits: 00 to 03, 04 to 07
Four digits: 00 to 03
When only 4 digits are read,
only word D is used.
Name Label Operation
Error Flag ER OFF
I
O
D
C1
C2
DSW(210)
3
104
D0
#0001
D32001
P_On
Always ON Flag
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