Writing The Control Program - Automation Direct DL405 User Manual

10–14
F4-08THM 8-Channel Thermocouple Input

Writing the Control Program

Multiple Active
Channels
Analog Data
and Sign Bits
After you have configured the F4–08THM module, use the following examples to
get started writing the control program.
The analog data is multiplexed into the lower word and is presented in 16 bits. The
upper word contains three groups of bits that contain active channel status, unused
bits, and broken transmitter status.
The control program must determine which channel's data is being sent from the
module. If you have enabled only one channel, its data will be available on every
scan. Two or more channels require demultiplexing the lower data word. Since the
module communicates as X input points to the CPU, it is very easy to use the active
channel status bits in the upper word to determine which channel is being
monitored.
V40402
MSB
X X X
5 5 4
7 0 7
Broken Unused
Transmitter
Bits
The first 16 bits represent the analog
data in binary format. The MSB is the
sign bit.
Bit Value Bit
0 1
1 2
2 4 10
3 8 11
4 16 12
5 32 13
6 64 14
7 128 15
F4–08THM
8pt 8pt 32pt
Input Input Input
X0 X10 X20
– – –
X7 X17 X57
V40400
LSB MSB
X X
4 3
0 7
Active
Bits Channel Sign Bit
Bits
MSB
Value
1 1
8 256
5 4
9 512
1024
X
2048
3
4096
7
8192
16384
32768
16pt 16pt 16pt
Input Output Output
X60
–
X77
V40403
V40401
LSB
X X
3 2
0 7
Data word contains 15
data bits and sign bit
V40401
1 1 1 1 9 8 7 6 5 4 3 2 1
3 2 1 0
= data bits
= sign bit
X
2
0
LSB
0
X
2
0