UPD17P136ACT datasheet(93/292 Pages) NEC

93 / 292 page

CHAPTER 9 REGISTER FILE (RF)

Caution should especially be taken with regard to the following point:

•

When using a symbol to define the control register as an address in data memory, it needs to be defined

as addresses 80H to BFH of BANK0.

Since the control register is manipulated using the window register, any attempt to manipulate the control register

other than by using the “PEEK” and “POKE” instructions needs to cause an error in the assembler.

However, note that any address in the area of the register file overlapping with data memory (addresses 40H to

7FH) can be defined as a symbol in the same manner as with normal data memory.

An example is given below.

Example 2.

RF71

MEM

1.71H

; Register file overlapping with data memory

RF02

MEM

0.82H

; Control register

BANK0

PEEK

WR, RF71

; RF71 becomes address 71H in BANK0.

PEEK

WR, RF02

; RF02 becomes address 02H in the control register.

BANK1

PEEK

WR, RF71

; RF71 becomes address 71H in BANK1.

PEEK

WR, RF02

; RF02 becomes address 02H in the control register.

The assembler (AS17K) has the below flag symbol manipulation instructions defined internally as macros.

SETn

: Set a flag to 1

CLRn

: Reset a flag to 0

SKTn

: Skip when all flags are 1

SKFn

: Skip when all flags are 0

NOTn

: Invert a flag

INITFLG

: Initialize a flag

By using these embedded macro instructions, the contents of the register file can be manipulated in 1-bit unit.

Due to the fact that most of control register consists of 1-bit flags, the assembler (AS17K) has reserved words for

use with these flags.

However, note that there is no reserved word for the stack pointer for its use as a flag. The only reserved word

used for the stack pointer is the reserved word “SP”, for its use as data memory. For this reason, none of the above

flag manipulation instructions can be used with the stack pointer.

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