GE PACSystems RX7i - Page 161

Chapter 4. Ladder Diagram (LD) Programming
146 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C
Operands for BUS READ
Parameter
Description
Allowed Operands
Optional
Length (??)
The number of BYTEs, DWORDs, or WORDs.
1 to 32,767.
Constant
No
R
Rack number. UINT constant or variable.
All except %S—%SC
No
S
Slot number. UINT constant or variable.
All except %S—%SC
No
SS
Subslot number (defaults to 0). UINT
constant or variable.
All except %S—%SC
Yes
RGN
Region (defaults to 1). WORD constant or
variable.
All except %S—%SC
Yes
OFF
The offset in bytes. DWORD constant or
variable.
All except %S—%SC
No
ST
The status of the operation. WORD
variable.
All except variables located in %S—%SC,
and constants
Yes
Q
Reference for data read from the module.
DWORD variable.
All except variables located in %S—%SC,
and constants
No
BUS_RD Status in the ST Output
The BUS_RD function returns one of the following values to the ST output:
0
Operation successful.
1
Bus error
2
Module does not exist at rack/slot location.
3
Module at rack/slot location is an invalid type.
4
Start address outside the configured range.
5
End address outside the configured address range.
6
Absolute address even but interface configured as odd byte only
8
Region not enabled
10
Function parameter invalid.