Automation Direct D0-DCM, Manual

Page: 52 / 70

Getting Started
User Application
Guidelines
RLL
Programming
for Communications
4–14
RLL Programming for Communications
DL05/06 Data Communications Module, 1st Edition, 08/05
Truth Table C52 C51 C50
First RX/WX 0 0 0
Second RX/WX 0 0 1
Third RX/WX 0 1 0
Fourth RX/WX 0 1 1
Fifth RX/WX 1 0 0
Sixth RX/WX 1 0 1
Seventh RX/WX 1 1 0
Eighth RX/WX 1 1 1
LD
K214
LD
K2
LDA
O40600
WX
VC100
SP122
RST
C51
C51
C50
SET
C50
C50 and C51 are interlocking
contacts. They are normally closed in
this rung to permit power flow to the
first WX instruction. Both bits are off,
corresponding to the first row of the
truth table.
After the WX instruction is executed
C50 is SET (turned on) which opens
the contact in this rung and closes the
C50 contact in the next rung.
C51 is RESET (turned off) which
leaves the C51 contact closed for the
next rung.
First RX/WX
Instruction
Our three RX/WX instructions can be
sequenced by the two contacts C50
and C51. Two contacts provide four
different binary states:
S
both off
S
C50 on and C51 off
S
C50 off and C51 on
S
both on
We only need to use three of the four
binary states (circled) since we only
have three RX/WX instructions to
sequence.