Yaskawa 545 PLC - Manual (Page 8)

4 OPERATION
7 Programming the PAC Blocks
4/12/94
An example may help clarify the above. Let’s assume we want to input
discrete data from the Texas Instruments PLC and output 1 word of analog
data to the PLC. Base 2 is not used by a real base, so we can choose that as
our simulated base. In the Texas Instruments Traffic Cop for base 2, slot 1, we
enter a 16Y discrete output module. In slot 2 of the same rack we enter a
8WX register input module. There is no special reason for choosing base 2 or
slots 1 & 2.
The PAC program is responsible for supplying the PLC with information about
where the simulated modules are located. After power-up, the node(s) on the
MicroTrac LAN that want to read/write data to the Texas Instruments PLC
must send the following messages:
A Remote Logic Input Configuration (Message Type 12) with the
CHANNEL NUMBER equal to 021. The LOGIC MASK value reflects the
bits you want to access.
A Remote Numeric Allocation Request (Message Type 11) with
CHANNEL NUMBER equal to 022, SUB CHANNEL NUMBER equal to 1
for the first word of the analog module.
When the PLC Gateway receives these messages, it requests a confirmation
from the Texas Instruments PLC to confirm that base 2 has a 16Y module in
base 2, slot 2. Once this is confirmed, data can be exchanged.
The node number used by the PAC block to address the PLC gateway is
usually 200. As mentioned previously, check the system schematic for
confirmation.
Each Channel of a Texas Instruments analog module uses one 16 bit word.
The word is presented to the Texas Instruments PLC as a two’s complement
binary number (also called a signed integer). These numbers can range from
+32767 to –32768. Each integer value has an assumed fixed location for the
decimal point (DP). Since the number transferred to or from the PLC is an
integer, there must be some way of determining in the PAC block where the
decimal point is located. In numeric PAC blocks (NUMI and NUMO) this in
accomplished by the DP (decimal point) parameter. For example, if the
integer transferred from the PLC to a PAC block has a range of +32.767 to
–32.768, the DP parameter for that PAC NUMI block must be specified as
three (3).
When entering a discrete module into the Traffic Cop program of the Texas
Instruments PLC, a reference number must also be entered. For discrete
output points, the reference numbers are in the range Y0001 to Y2048; discrete
input points range from X0001 to X2048. So if a discrete input module (16X)
were entered into the Traffic Cop, X0001 would be entered as the reference
number. The PLC then reserves X0002 through X0016 for the other points in
Example
Node Number
Format of
Numeric Data
Format of Logic
Data
RD 3056-10