Status indicators, Diagnostic codes returned by the module – Rockwell Automation 1794-VHSC Very High Speed Counter Module Installation Instruction User Manual
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Publication 1794-IN067C-EN-P - January 2012
Status Indicators
This module has one red/green power/status indicator (OK), and one yellow 
indicator for each input and output. The I/O status indicators are multiplexed 
in 2 groups (A0, B0, Z0, O0, O1); and (A1, B1, Z1, O2, O3) at a frequency of 
488 Hz. If inputs or outputs change at or near that frequency, the indicators 
will vary in brightness. 
When an active indicator (yellow) is lighted, a valid signal (active high or active low) 
is present at the input terminals.
The module power/status indicator (OK) shows power applied to the module, and 
the status of the module.
Diagnostic Codes Returned by the Module
If an incomplete, incorrect or conflicting set of configuration parameters is sent to 
the module, the PE bit is asserted, the green module status indicator flashes, and an 
error code is displayed in bits 0…11 of the module/channel status word. The codes 
are identified below. Use a CIO instruction to access this information. 
During hardware self-tests, when either FlexBus power or terminal base power is 
first applied and a fatal error occurs, the TF bit is asserted and the red 
module/power status indicator comes on. An error code is placed in the lower byte 
of the module/channel status word to indicate the failed resource. Use a CIO 
instruction to access this information. When using the CIO instruction, this would 
be word 10.
0
Z
F
B
F
AF
Filter
Description
0
0
0
0
No filter
0
0
0
1
50 kHz (10
μs + 0 μs/-1.6 μs)
0
0
1
0
5k Hz (100
μs + 0 μs/-13.2 μs)
0
1
0
0
500 Hz (1.0 ms + 0 ms/-125
μs)
1
0
0
0
50 Hz (10.0 ms + 0 ms/-1.25 ms)
0
A input not filtered
1
A input filtered
0
B input not filtered
1
B input filtered
0
Z input not filtered
1
Z input filtered
Status Indicators
Indicator
Indication
Explanation
A (status of input A
Yellow
Input A active
Off
Input A not active
B (status of input B
Yellow
Input B active
Off
Input B not active
Z (status of input Z
Yellow
Input Z active
Off
Input Z not active
Out 0, 1, 2, 3
Yellow
Output is on
Off
Individual output is off
Indicator
Indication
Explanation
OK
Solid red
• Hardware diagnostic error, TF set to 1 and
module/channel status contains error code
• Hardware runtime failure (that is, watchdog
timeout), module communication ceases
Flashing red
• Module is configuring hardware, NR is set to 1.
• Module is in test mode (bits 8…15 of counter 
control word are nonzero), TF set to 1
Flashing red 
(with occasional 
flashing green)
• Module 24V power is below minimum rating.
Solid green
• Module is active and acting normally
Flashing green
• Module is not configured
• Programming error, PE is set to 1 and error code 
is supplied in bits 0…11 of module/channel 
status word
• Field power fault, FP set to 1
• Adapter powered down, and module local 
power still active
• ControlNet cable disconnected
• PLC in PROG mode
Filter Selection (Configuration Word 1)
VERY HIGH SPEED COUNTER MODULE
1794-VHSC
A
B
Z
A
B
Z
Allen-Bradley
1
OUT
0
1
2
3
OUT
0
A
B
A = Status Indicators
B = Power Indicator
Diagnostics Reported by Input Data Word 8
Read Word
Bit
Indication
Word 8
00
A reserved configuration or mode was programmed.
01
ZF/BF/AF were selected and no filter was programmed, or multiple filters were 
selected.
02
A timebase was entered that was not a multiple of 10, or the timebase is out of 
range (>3000, that is 3 s).
03
A configuration requiring a timebase was selected and no gate interval was set, 
or the gate interval is out of range (>3 s) or the product of timebase and gate 
interval is greater than 3 s.
04
A rollover of zero was programmed through PWM was not selected; a rollover 
was programmed and PWM was selected; or the rolloveris out of range (1 < 
rollover < 16,777,216).
Word
05
The preset (1 < preset < 16,777,216) is out of range.
06
A configuration was selected that requires a scalar, and no scalar was 
programmed or multiple scalars were selected.
07
A tie has been connected to an unprogrammed window.
08
Counter 0 window ON and OFF values are equal and not zero or counter 0 
window ON and OFF value greater than16,777,215.
09
Counter 1 window ON and OFF values are equal and not zero or counter 1 
window ON and OFF value greater than16,777,215.
10
Reserved
11
Word 9 Bit Description
Read 
Word
Bit
02
01
00
Dec.
Definition
Word 8
00…07
0
0
1
1
RAM test failed
0
1
0
2
ROM checksum test failed
0
1
1
3
EEPROM test failed
1
0
0
4
Programmable Gate Array 
loading failed
All other combinations not used