Honeywell VC4 User Manual page 151

Get Filter Life - 0x44
This command returns the user's settings for total filter lifetime. Lifetime is set by the user to
indicate how often the filters should be changed. A maintenance fault will be issued when the
filters are this old. The valid range is 30 to 365 days. Zero lifetime means a filter maintenance.
Command Packet to slave:
Command Code (0x44) - 1 byte
Response from slave:
Command code (0x44) - 1 byte
VC4™ date - 2 bytes
VC4™ time - 2 bytes
Internal filter life - 2 bytes
External filter life - 2 bytes
Status - 1 byte (always 0x00 as currently implemented)
Get Floating Status - 0x45
This packet returns general information about the slave. It combines the information of packet
0x37 (Get Point Status) and 0x31 (Get Unit Status). However, it reports the concentration in
IEEE floating-point format instead of as a scaled integer. Since it provides information that
would otherwise require five interrogations, this should permit faster polling of slaves on a
multidrop RS-485 bus.
Command Packet to Slave:
Command Code (0x45) - 1 byte
Response from Slave:
Command code (0x45) - 1 byte
VC4™ date - 2 bytes
VC4™ time - 2 bytes
Status - 1 byte
0x01 - in monitor
0x02 - maintenance fault relay activated
0x04 - instrument fault relay activated
0x08 - (1 bit) undefined
0x10 - A new fault has occurred since the last time packet 0x3D (Get Fault History) was
requested.
0x20 - A new alarm has occurred since the last time packet 0x36 (Get Alarm History) was
requested.
0xC0 - (2 bits) undefined
(The 7 byte Point Structure repeats 4 times)
VC4™ 151 User Manual