GE PACSystems RX7i - Page 165

Chapter 4. Ladder Diagram (LD) Programming
150 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C
BUS Write
When the BUS_WRT function receives power flow through its enable
input, it writes the data located at reference (IN) to the module at the
specified rack (R), slot (S), subslot (SS) and optional address region
(RGN) and offset (OFF). BUSWRT writes the specified length (LEN) of
data units (DWORDS, WORDs or BYTEs).
The BUS_WRT function passes power to the right when its operation
is successful. The status of the operation is reported in the status
location (ST).
Note: For each BUS_WRT function type, use the corresponding data
type for the IN operand. For example, BUS_WRT_BYTE
requires IN to be a BYTE variable.
Note: An interrupt block can preempt the execution of a BUS_WRT
function. On the bus, only 256 bytes are written coherently
(i.e., written without being preempted by an interrupt).
Mnemonics:
BUS_WRT_DINT
BUS_WRT_DWORD
BUS_WRT_WORD
Operands for Bus Write
Parameter
Description
Allowed
Optional
Length (??)
Length. The number of BYTEs, DWORDs, or WORDs. 1 to
32,767.
Constant
No
IN
Reference for data to be written to the module. DWORD
variable.
All except variables
located in %S—%SC,
and 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 constant
Yes