SN8P1700
8-bit micro-controller build-in 12-bit ADC
WORKING REGISTERS
The locations 80H to 85H of RAM bank 0 in data memory stores the specially defined registers such as register H, L, R,
X, Y, Z, respectively shown in the following table. These registers can use as the general purpose of working buffer
and be used to access ROM’s and RAM’s data. For instance, all of the ROM’s table can be looked-up with R, X, Y and
Z registers. The data of RAM memory can be indirectly accessed with H, L, Y and Z registers.
80H
L
81H
H
82H
R
83H
Z
84H
Y
85H
X
RAM
R/W
R/W
R/W
R/W
R/W
R/W
H, L REGISTERS
The H and L are 8-bit register with two major functions. One is to use the registers as working register. The other is to
use the registers as data pointer to access RAM’s data. The @HL that is data point_0 index buffer located at address
E6H in RAM bank_0. It employs H and L registers to addressing RAM location in order to read/write data through ACC.
The Lower 4-bit of H register is pointed to RAM bank number and L register is pointed to RAM address number,
respectively. The higher 4-bit data of H register is truncated in RAM indirectly access mode.
H initial value = 0000 0000
081H
H
Bit 7
HBIT7
R/W
Bit 6
HBIT6
R/W
Bit 5
HBIT5
R/W
Bit 4
HBIT4
R/W
Bit 3
HBIT3
R/W
Bit 2
HBIT2
R/W
Bit 1
HBIT1
R/W
Bit 0
HBIT0
R/W
L initial value = 0000 0000
080H
L
Bit 7
LBIT7
R/W
Bit 6
LBIT6
R/W
Bit 5
LBIT5
R/W
Bit 4
LBIT4
R/W
Bit 3
LBIT3
R/W
Bit 2
LBIT2
R/W
Bit 1
LBIT1
R/W
Bit 0
LBIT0
R/W
ꢃExample: If want to read a data from RAM address 20H of bank_0, it can use indirectly addressing mode to
access data as following.
B0MOV
B0MOV
B0MOV
H, #00H
L, #20H
A, @HL
; To set RAM bank 0 for H register
; To set location 20H for L register
; To read a data into ACC
ꢃExample: Clear general-purpose data memory area of bank 0 using @HL register.
CLR
H
; H = 0, bank 0
MOV
B0MOV
A, #07FH
L, A
; L = 7FH, the last address of the data memory area
CLR_HL_BUF:
END_CLR:
CLR
DECMS
JMP
@HL
L
CLR_HL_BUF
; Clear @HL to be zero
; L – 1, if L = 0, finish the routine
; Not zero
CLR
@HL
; End of clear general purpose data memory area of bank 0
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