CHECKING SYSTEM STATUS
SNAP PAC Redundancy Option User’s Guide
50
Using the Memory Map to Enter and Exit Maintenance Mode
To exit or enter maintenance mode programmatically in a PAC Control strategy, use the PAC Control
command Write Number to I/O Unit Memory Map with the memory map address 0xF8001000. Use
either a hexadecimal or ASCII value from the following table for the desired command.
Command
Hexadecimal Value
ASCII Value
Enter Maintenance
0x4D
M
Exit Maintenance (become active)
0x4241
BA
Exit Maintenance (reset)
0x52
R
Entering Maintenance Mode on Boot
The memory map address 0xF8001004 reads/writes the Enter Maintenance Mode flag. Use the PAC
Control command Read
Number from I/O Unit Memory Map to read this memory location. If this
flag is TRUE, on boot the controller will enter maintenance mode.
To set the Enter Maintenance Mode flag to TRUE, write the value 0x4D41494E (hex) or MAIN (ASCII)
to memory map address 0xF8001004. The controller will enter maintenance mode on boot. If any
other value is used, it won’t enter maintenance mode.
Redundant System State Machine
You can use the information below to better understand the PAC Redundancy Manager status
messages and the sequence in which some system states occur. Messages appear in PAC
Redundancy for each of the redundant controllers. For definitions of the status messages, see the
previous section,
“Redundant System Status Messages.”
Maintenance
2
Online: Non-Candidate
3
Backup: Non-Qualified
4
Online: Candidate
5
Update Complete
6
Backup: Qualified Connected
7
Cold Start
8
Failover Start
9
Active
10
Backup: Qualified Disconnected
11
State
Value (Decimal)
