Allen-Bradley 1746-NT8 - Monitoring Channel Status Bits Example

Publication 1746-UM022B-EN-P - January 2005
Programming Examples 5-9
Monitoring Channel Status Bits Example
S:1
15
COP
Copy File
Source #N10:0
Dest #O:1.0
Length 8
COP
#NT8_CH_CNF
FLL
Fill File
Source 0
Dest #N10:20
Length 8
FLL
#NT8_CH0_STS_FLAGS
CLR
Clear
Dest B3:7
0000000000000001<
CLR
B3:6
4
NT8_CHECKING_STS
COP
Copy File
Source #I:1.0
Dest #N10:30
Length 8
COP
#NT8_LAST_TEMP_READ
T11:0
DN
NT8_STS_CHECK_TMR/DN
EN
DN
TON
Timer On Delay
Timer T11:0
Time Base 1.0
Preset 60<
Accum 10<
TON
NT8_STS_CHECK_TMR
T11:0
DN
NT8_STS_CHECK_TMR/DN
L
B3:6
4
NT8_CHECKING_STS
COP
Copy File
Source #N10:10
Dest #O:1.0
Length 8
COP
#NT8_CH_CNF
B3:6
4
NT8_CHECKING_STS
EN
DN
TON
Timer On Delay
Timer T11:1
Time Base 1.0
Preset 7<
Accum 0<
TON
NT8_STS_CNF_TMR
0004
0000
0001
0002
0003
During 1st program scan, copy thermocouple channel configuration words (N10:0 - N10:7) to NT8. In addition, initialize
channel error registers (N10:20 - N10:27) and Error Flags (B3/119).
If the NT8 is not checking channel status, store the thermocouple readings in the NT8 last channel reading registers
(N10:37). These registers should be used in the remainder of the program (e.g. for temperature control) instead of the
NT8 I/O image location.
T11:0 is a repeating 60-second timer which initiates the NT8 channel status check.
Every 60 seconds, initiate a NT8 channel status check by latching the NTB channel status checking bit and copying
the “Status check” configuration words (N10:10 -N10:7) to the NT8 configuration words.
After copying the “Status Check configuration words” start a 7-second timer (T11:1) to allow the NT8 to update its I/O
image to the channel status words. The time required for the NT8 to update its I/O image is dependent on the NT8
configuration. Note, the time required to be greater than the channel update time including the auto calibration time.