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4-110 Series 90-30/20/Micro Programmable Controllers Reference Manual – September 1998 GFK-0467K
4
The function passes power to the right whenever power is received, unless:
• Not all references of the type specified are present within the selected range.
• The CPU is not able to properly handle the temporary list of I/O created by the function.
• The range specified includes I/O modules that are associated with a “Loss of I/O” fault.
_____
| |
(enable) —|DO
_
IO|— (ok)
| |
| |
| |
(starting address) —|ST |
| |
| |
(ending address) -|END |
| |
| |
—|ALT |
|_____|
Parameters:
Parameter Description
enable When the function is enabled, a limited input or output scan is performed.
ST ST is the starting address or set of input or output points or words to be serviced.
END END is the ending address or set of input or output points or words to be serviced.
ALT For the input scan, ALT specifies the address to store scanned input point/word values.
For the output scan, ALT specifies the address to get output point/word values from to
send to the I/O modules. For Model 331 and later CPUs, the ALT parameter can have
an effect on speed of DOIO function block execution (see Note below and the section on
the enhanced DO I/O function for 331 and later CPUs on page 4-110).
ok The ok output is energized when the input or output scan completes normally.
Note
For Model 331 and later CPUs, the ALT parameter of the DOIO function block can be used to enter
the slot of a single module in the main rack. When that is done, the DOIO function block will
execute in 80 microseconds instead of the 236 microseconds required when the block is
programmed without the ALT parameter. No error checking is performed to prevent overlapping
reference addresses or module type mismatches.
Valid Memory Types:
Parameter flow %I %Q %M %T %S %G %R %AI %AQ const none
enable •
ST • • • •
END • • • •
ALT • • • • • • • • •
ok • •
• Valid reference or place where power may flow through the function.