SONIX SN8P2977, User Manual

Page: 37 / 146

SN8P2977
8-Bit Micro-Controller with Regulator, PGIA, 24-bit ADC
SONiX TECHNOLOGY CO., LTD
Page 37
V1.7
2.1.11
H, L REGISTERS
The H and L registers are the 8-bit buffers. There are two major functions of these registers.

can be used as general working registers

can be used as RAM data pointers with @HL register
081H Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
H HBIT7 HBIT6 HBIT5 HBIT4 HBIT3 HBIT2 HBIT1 HBIT0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
After reset 0 0 0 0 0 0 0 0
080H Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
L LBIT7 LBIT6 LBIT5 LBIT4 LBIT3 LBIT2 LBIT1 LBIT0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
After reset 0 0 0 0 0 0 0 0

Example: Uses H, L register as the data pointer to access data in the RAM address 020H of bank0.
B0MOV H, #00H ; To set RAM bank 0 for H register
B0MOV L, #20H ; To set location 20H for L register
B0MOV A, @HL ; To read a data into ACC

Example: Uses the H, L register as data pointer to clear the RAM data.
B0MOV H #0 ; H = 0, bank 0
B0MOV L, #07FH ; L = 7FH, the last address of the data memory area
CLR_HL_BUF:
CLR @HL ; Clear @HL to be zero
DECMS L ; L
– 1, if Z= 0, finish the routine
JMP CLR_HL_BUF ; Not zero
CLR @HL
END_CLR: ; End of clear general purpose data memory area of bank 0
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