APC UPS control system - Manual (Page 196)

Register 1
All bits are valid on the Matrix UPS. SmartUPS models only support bits
6 and 7. Other models do not respond.
Bit Hex
Bit Meaning
0 0x01 In wakeup mode (typically lasts < 2s)
1 0x02 In bypass mode due to internal fault - see register 2 or 3
2 0x04 Going to bypass mode due to command
3 0x08 In bypass mode due to command
4 0x10 Returning from bypass mode
5 0x20 In bypass mode due to manual bypass control
6 0x40 Ready to power load on user command
7 0x80 Ready to power load on user command or return of line power
Register 2
Matrix UPS models report bits 0-5. SmartUPS models only support bits 4
and 6. SmartUPS v/s and BackUPS Pro report bits 4, 6, 7. Unused bits
are set to 0. Other models do not respond.
Bit Meaning
0 Fan failure in electronics, UPS in bypass
1 Fan failure in isolation unit
2 Bypass supply failure
3 Output voltage select failure, UPS in bypass
4 DC imbalance, UPS in bypass
5 Command sent to stop bypass with no battery connected - UPS still in
bypass
6 Relay fault in SmartTrim or SmartBoost
7 Bad output voltage
Register 3
All bits are valid on the Matrix UPS and 3rd generation SmartUPS models.
SmartUPS v/s and BackUPS Pro models report bits 0-5. All others report
0-4. State change of bits 1,2,5,6,7 are reported asynchronously with ? and
195