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Format Code - 1 byte
Revision # - 1 byte (1-255) (always filled)
Status
0x00 = Read OK
0x01 = Invalid Gas # index
0xff = Bad read
Get Fault History - 0x3D
This command will query the unit for the latest fault(s). There can be as many as four and as
few as zero faults. General system faults are indicated by bit 0 of the point status byte. If bit 0 is
set to 1, bits 1-2 should be ignored. The point status byte is invalid for Fault 17 (Voltage Fail)
and Fault 18 (Relay Fail).
Command packet to instrument:
Command Code (0x3D) - 1 byte
Response packet from instrument:
Command Code (0x3D) - 1 byte
VC4™ Date - 2 bytes
VC4™ Time - 2 bytes
# of faults - 1 byte (0-4 maximum) (fault data, maximum of four possible)
Date of fault - 2 bytes
Time of fault - 2 bytes
Fault # -1 byte
Point Status -1 byte
bit 0: General fault bit
0 = point specific
1 = general
bits 1-2: Point # where fault occurred
(ignored if bit 0 is 1 and for Flts 17 and 18)
00 = Point 1
01 = Point 2
10 = Point 3
11 = Point 4
bits 3-5: Undefined
bit 6: Previously Read
0 = new (not previously read)
VC4™
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User Manual
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