High−level Instructions
3 − 262
Description
The 16−bit data specified by S will be stored in the FIFO buffer headed by the area specified by D.
D should specify the beginning of the FIFO buffer defined by the F115 (FIFT) instruction.
The specified data is written to the address indicated by the writing pointer when the instruction is executed.
D
D+1
D+2
15 0
(0)
(n−1)
(n−2)
[S]
Memory size of FIFO buffer
Number of stored data items (words)
Writing pointer (lower)
Data storage area
▲Writing pointer
・(0), (n−2) and (n−1) are addresses
assigned to the data storage areas.
・n is the value specified by the F115 (FIFT)
instruction.
The writing pointer is stored in the lower eight bits of the third word of the FIFO buffer area, and is indicated by
a relative position in the data storage area.
The actual address is the value of the leading address in the FIFO buffer area specified by D, plus 3, plus the
value of writing pointer (the value of which only the lower byte is a decimal value).
When the writing is executed, 1 is added to the number of stored data items, and the writing pointer is
incremented by 1.
Notes
An error occurs if this is executed when the FIFO buffer is full
(the number of stored data items = the size n of the FIFO
defined by the FIFT instruction). Writing is inhibited.
If this is executed when the writing pointer is indicating the
final address in the FIFO buffer (the ”n” value defined by the
FIFT instruction), the writing pointer will be set to 0.
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