UPD17P136ACT datasheet(92/292 Pages) NEC

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CHAPTER 9 REGISTER FILE (RF)

•

WDTRES

(RF: 03H, bit 3)

•

WDTEN

(RF: 03H, bit 0)

•

TM0RES

(RF: 11H, bit 2)

•

TM1RES

(RF: 12H, bit 2)

•

BTMRES

(RE: 13H, bit 2)

•

ADCSTRT (RF: 20H, bit 0)

Within the four bits of data in a nibble, there are bits which are fixed at 0 and will therefore always be read as 0.

These bits remain fixed at 0 even when an attempt is made to write to them.

Attempting to read data in the unused register address area (38 nibbles) will yield unpredictable values. In addition,

attempting to write to this area has no effect.

9.4 NOTES CONCERNING USE OF THE REGISTER FILE

9.4.1 Notes Concerning Operation of the Control Register (Read-Only and Unused Registers)

It is necessary to take note of the following notes concerning device operation and use of the 17K Series assembler

(AS17K) and in-circuit emulator (IE-17K or IE-17K-ET) with regard to the read-only (R) and unused registers in the

control register (register file addresses 00H to 3FH).

(1) Device operation

Writing to a read-only register has no effect.

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

to write to an address in the unused data area has no effect.

(2) During use of the assembler (AS17K)

An error will be generated if an attempt is made to write to a read-only register.

An error will also be generated if an attempt is made to read from or write to an address in the unused data

area.

(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. No error is generated.

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

to write to an address in the unused data area has no effect. No errors are 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 an error to be generated

PEEK

WR, 02H

;

POKE

21H, WR

;

Case in which no error is generated

RF71

MEM0.71H

; Symbol definition

PEEK

WR, RF71 ;

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