High−level Instructions
3 − 255
Description
This defines the area used as the FIFO buffer. A data storage area of n words (n = K1 to K256) is defined for
the area specified by D.
Definition of the area using the F115 (FIFT) instruction should be carried out only once, before writing to or
reading from the FIFO buffer. Normally, reading and writing are disabled while this instruction is being
executed.
When the F115 (FIFT) instruction is executed, the FIFO buffer area is defined as follows.
K0
0
KnD
D+1
D+2
15 0
D+3
D+2+n
n−2
n−1
0
1
15 0
Reading pointer
(0 to 255/H00 to HFF)
Writing pointer
(0 to 255/H00 to HFF)
0
Data
storage
area
(n words)
Memory size of FIFO buffer (n)
Number of stored data items (words)
FIFO pointer
When the F115 (FIFT) instruction is executed, the following are stored as default values: D = n (the value
specified by the F115 (FIFT) instruction), D+1 = K0, and D+2 = H0000.
Flag conditions
・Error flag (R9007): Turns on and stays on when:
・Error flag (R9008): Turns on for an instant when:
− The area specified using the index modifier exceeds the limit.
− n=0.
− n > 256.
− The area specified by n exceeds the limit.
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