TMP89FS60 datasheet(72/410 Pages) TOSHIBA

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Page 58

3. Interrupt Control Circuit

3.5 Interrupt Sequence

TMP89FS60

RA003

3.5.3.2

Using data transfer instructions

To save only a specific register without nested interrupts, data transfer instructions are available.

Figure 3-4 Saving/Restoring General-purpose Registers under Interrupt Processing

3.5.3.3

Using a register bank to save/restore general-purpose registers

In non-multiple interrupt handling, the register bank function can be used to save/restore the general-

purpose registers at a time. The register bank function saves (switches) the general-purpose registers by

executing a register bank manipulation instruction (such as LD RBS,1) at the beginning of an interrupt

service task. It is unnecessary to re-execute the register bank manipulation instruction at the end of the

interrupt service task because executing the RETI instruction makes a return automatically to the register

bank that was being used by the main task according to the content of the PSW.

Note: Two register banks (BANK0 and BANK1) are available. Each bank consists of 8-bit general-purpose

registers (W, A, B, C, D, E, H, and L) and 16-bit general-purpose registers (IX and IY).

Example :Save/store register using data transfer instructions

PINTxx:

(GSAVA), A

; Save A register

Interrupt processing

A, (GSAVA)

; Restore A register

RETI

; RETURN

Example :Saving/restoring registers, using an instruction for transfer with data memory (with the main task using the regis-

ter bank BANK0)

PINTxx:

RBS, 1

; Switches to the register bank BANK1

Interrupt processing

RETI

; RETURN

(Makes a return automatically to BANK0 that

was being used by the main task when the

PSW is restored)

Main task

Interrupt acceptance

Interrupt

service task

Saving

registers

Restoring

registers

Interrupt return

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