12 - 75
(16) For redundant systems (Other system CPU information 
*1
)
SD1600 to SD1659 is only valid during the back up mode for redundant systems, and 
refresh cannot be done when in the separate mode.
SD1651 to SD1699 are valid in either the backup mode or separate mode.
When a stand-alone system SD1600 to SD1699 are all 0.
*2: Shows the special register (SD ) for the host system CPU module.
Table12.35 Special register
Number Name Meaning Explanation
Set by 
(When Set)
Corres-
ponding 
ACPU 
SD *2
Corresponding 
CPU
SD1600
System error  
information
System error  
information
• If an error is detected by the error check for redundant system, the 
corresponding bit shown below turns ON. That bit turns OFF when the 
error is cleared after that.
• If any of b0, b1, b2 and b15 is ON, the other bits are all OFF.
• In the debug mode, b0, b1, b2 and b15 are all OFF.
S(Every END)
–
QnPRH
SD1601
System 
switching 
results
System switching 
results
Stores the reasons for system switching.
• Stores the reasons for system switching into SD1601 of both systems 
when system switching occarred.
• Initialized to 0 at power OFF to ON/reset to unreset.
• The following shows values stored into this register.
0: Initial value (System switching has not occurred)
1: Power-OFF, Reset, H/W failure, WDT error,(*)
2: CPU stop error (except WDT)
3: System switching request by network module
16: System switching dedicated instruction
17: System switching request from GX Developer
*: When the system is switched by the power OFF/reset of the control 
system, "1" is not stored into SD1601 of the new standby system.
S(when system 
is switched)
SD1602
System  
switching  
dedicated  
instruction  
parameter
System switching 
dedicated 
instruction 
parameter
• Stores the parameters for system switching dedicated instruction 
SP.CONTSW.
(The parameters (SD1602) for SP.CONTSW are stored in both systems 
A&B)
• SD1602 is only valid when "16" is stored in SD1601.
• This SD1602 is updated once system switch instruction SP.CONTSW is 
activated.
S(when system 
is switched)
SD1610
Other system 
diagnostic error
Diagnostic error 
code
• The error value sorted in BIN code.
• Stores SD0 of the other system CPU module
S(Every END) SD0
SD1611 Other system 
diagnostic error  
occurrence  
time
Diagnostic error 
occurrence time
• Stores the date and time when diagnostics error occurred corresponding 
to error code stored in SD1610.
• Data format is the same as SD1 to SD3.
• Also, stores the value to SD1 to SD3.
S(Every END)
SD1 to 
SD3
SD1612
SD1613
SD1614
Other system 
error  
information  
category
Error information 
category code
• Stores the category code corresponding to the error comment 
information/individual information code.
• Data format is the same as SD4.
• Also, stores the value to SD4.
S(Every END) SD4
SD1615 
to 
SD1625
Other system 
error common  
information
Error common 
information
• Stores the common information corresponding to the error code stored 
in this system CPU.
• Data composition is the same as SD5 to SD15.
• Also, stores the value to SD5 to SD15.
S(Every END)
SD5 to 
SD15
SD1626
to 
SD1636
Other system 
error individual  
information
Error individual 
information
• Stores the individual information corresponding to the error code stored 
in this system CPU.
• Data composition is the same as SD16 to SD26.
• Also, stores the value to SD16 to SD26.
S(Every END)
SD16 to 
SD26
b1 b0b15 b2
Fixed to 0
Tracking cable is not 
connected or damaged
Each bit
0: OFF
1: ON
Power-OFF, reset, 
watchdog timer error or 
hardware failure occurred 
in other system
Bit turns on when failing to 
connect with other system. 
The following
 causes are 
shown below:
Tracking H/W failure
Host system WDT 
error
Cannot recognize 
other system therefore 
causing error
SD1600
Other system stop error 
(except watchdog timer 
error)