Allen-Bradley A-B QUALITY DL20 Series User Manual page 85

Example Message Trigger
with Variable Data
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
MS0
MSI
t0
t0: The high order bits of the first variable are set up on the data
lines; they are zero in this case, then MS1 is turned ON.
t1: The DL20 stores a zero, the value on the data lines, as the high
order byte of a variable. Steps t0 and t1 are optional; if low
order data is strobed in without high order data having been
strobed in, the DL20 will assume that the high order data is zero.
t2: MS1 is turned OFF; then the low order bits of the first variable
are set up on the data lines, 100 in this case, then MS0 is turned
ON.
t3: The DL20 stores 100, the value on the data lines, as the low
order byte of a variable. Both the high order and low order
portion of a variable have now been read in, so the DL20 queues
the variable up. In this case, the value 100 is queued up.
t4: First MS0 is turned OFF; then the high order bits of the second
variable are set up on the data lines, zero in this case; the MS1
is turned ON.
Message number 12 contains two variables.
PARTS COUNT =
First, transfer over the parts count, 8 bits at a time. Then transfer over the
reject count, 8 bits at a time. Lastly, transfer over the message number,
which triggers the message. The timing of the message would look like this:
t1 t2 t3
REJECTS =
t4 t5 t6
t5: The DL20 stores zero, the value on the data lines, as the high
order byte of a variable. Once again, t4 and t5 are optional.
t6: First MS1 is turned off; then the low order bits of the second
variable are set up on the data lines, 8 in this case; then MS0 is
turned on.
t7: The DL20 stores 8, the value on the data lines, as the low order
byte of a variable. Both the high order and low order portion of a
variable have now been read in, so the DL20 queues the
variable up. In this case, the variable 8 is queued up.
t8: First MS0 is turned OFF; then the data lines are set to the value
12, which is the message number we wish to trigger; then both
MS0 and MS1 are turned ON.
t9: The value on the data lines, 12, is queued up as a message
trigger.
t10: MS0 and MS1 are turned OFF. The DL20 ignores the data lines.
Chapter 7
The Parallel Port
t7 t8 t9 t10
7–13