573
Table Data Processing Instructions Section 3-16
3-16-3 FIRST IN FIRST OUT: FIFO(633)
Purpose Reads the first word of data written to the specified stack (the oldest data in
the stack).
Ladder Symbol
Variations
Applicable Program Areas
Operands TB through TB+3: Stack control words
The first four words of the stack contain the PLC memory address of the last
word in the stack and the stack pointer (the PLC memory address of the next
word to be overwritten by PUSH(632)).
TB+4 through TB+(N–1): Data storage region
The remainder of the stack is used to store data.
FIFO(633)
TB
D
TB: First stack address
D: Destination word
Variations Executed Each Cycle for ON Condition FIFO(633)
Executed Once for Upward Differentiation @FIFO(633)
Executed Once for Downward Differentiation Not supported.
Immediate Refreshing Specification Not supported.
Block program areas Step program areas Subroutines Interrupt tasks
OK OK OK OK
15 0
TB
15 0
TB+1
15 0
TB+2
15 0
TB+3
PLC memory address of the last
word in the stack (rightmost 4 digits)
PLC memory address of the last
word in the stack (leftmost 4 digits)
Stack pointer (rightmost 4 digits)
Stack
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