SN8P2977
8-Bit Micro-Controller with Regulator, PGIA, 24-bit ADC
SONiX TECHNOLOGY CO., LTD
Page 36
V1.7
2.1.10
Y, Z REGISTERS
The Y and Z registers are the 8-bit buffers. There are three major functions of these registers.
can be used as general working registers
can be used as RAM data pointers with @YZ register
can be used as ROM data pointer with the MOVC instruction for look-up table
084H
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Y
YBIT7
YBIT6
YBIT5
YBIT4
YBIT3
YBIT2
YBIT1
YBIT0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
After reset
-
-
-
-
-
-
-
-
083H
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Z
ZBIT7
ZBIT6
ZBIT5
ZBIT4
ZBIT3
ZBIT2
ZBIT1
ZBIT0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
After reset
-
-
-
-
-
-
-
-
Example: Uses Y, Z register as the data pointer to access data in the RAM address 025H of bank0.
B0MOV
Y, #00H
; To set RAM bank 0 for Y register
B0MOV
Z, #25H
; To set location 25H for Z register
B0MOV
A, @YZ
; To read a data into ACC
Example: Uses the Y, Z register as data pointer to clear the RAM data.
B0MOV
Y, #0
; Y = 0, bank 0
B0MOV
Z, #07FH
; Z = 7FH, the last address of the data memory area
CLR_YZ_BUF:
CLR
@YZ
; Clear @YZ to be zero
DECMS
Z
; Z
– 1, if Z= 0, finish the routine
JMP
CLR_YZ_BUF
; Not zero
CLR
@YZ
END_CLR:
; End of clear general purpose data memory area of bank 0
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