D17133CS datasheet(91/289 Pages) NEC

91 / 289 page

CHAPTER 9

(3) During use of the in-circuit emulator (IE-17K or IE-17K-ET) (operation during patch processing and

similar operations)

Attempting to write to a read-only register has no effect and no error is generated.

Attempting to read data from an address in the unused data area will yield an unpredictable value.

Attempting to write to an address in the unused data area has no effect and no error is generated.

9.4.2 Register File Symbol Definitions and Reserved Words

Attempting to use a numerical value in a 17K Series assembler (AS17K) to specify a register file address in the

rf operand of the PEEK WR, rf or POKE rf, WR instructions will cause an error to be generated.

Therefore, as shown in Example 1, register file addresses need to be defined beforehand as symbols.

Example 1.

Case which causes and error to be generated

PEEK

WR, 02H

;

POKE

21H, WR

;

Case in which no error is generated

RF71

MEM

0.71H

; Symbol definition

PEEK

WR, RF71

;

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 commands needs to cause an error to be generated in the assembler (AS17K).

However, note that any address in the area of the register file overlapping with data memory (address locations

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

0.71H

; Address in register file overlapping with data memory

RF02

MEM

0.82H

; Control register

PEEK

WR, RF71

; RF71 becomes address 71H

PEEK

WR, RF02

; RF02 becomes address 02H in the control register.

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