SN8F22521B 参数 Datasheet PDF下载

SN8F2250B Series

USB 2.0 Full-Speed 8-Bit Micro-Controller

2.1.1.3 LOOK-UP TABLE DESCRIPTION

In the ROM’s data lookup function, Y register is pointed to middle byte address (bit 8~bit 15) and Z register is pointed

to low byte address (bit 0~bit 7) of ROM. After MOVC instruction executed, the low-byte data will be stored in ACC and

high-byte data stored in R register.

Example: To look up the ROM data located “TABLE1”.

B0MOV

B0MOV

MOVC

INCMS

JMP

INCMS

NOP

@@:

TABLE1:

MOVC

…

DW

DW

DW

…

Y, #TABLE1$M

Z, #TABLE1$L

; To set lookup table1’s middle address

; To set lookup table1’s low address.

; To lookup data, R = 00H, ACC = 35H

; Increment the index address for next address.

; Z+1

; Z is not overflow.

; Z overflow (FFH

00),

Y=Y+1

;

;

; To lookup data, R = 51H, ACC = 05H.

;

; To define a word (16 bits) data.

Z

@F

Y

0035H

5105H

2012H

Note: The Y register will not increase automatically when Z register crosses boundary from 0xFF to

0x00. Therefore, user must take care such situation to avoid loop-up table errors. If Z register

overflows, Y register must be added one. The following INC_YZ macro shows a simple method

to process Y and Z registers automatically.

Example: INC_YZ macro.

INC_YZ

MACRO

INCMS

JMP

INCMS

NOP

@@:

ENDM

Z

@F

Y

; Z+1

; Not overflow

; Y+1

; Not overflow

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