TMP86CS49FG datasheet(53/252 Pages) TOSHIBA

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TMP86CS49FG

3.3 Interrupt Sequence

An interrupt request, which raised interrupt latch, is held, until interrupt is accepted or interrupt latch is cleared to

“0” by resetting or an instruction. Interrupt acceptance sequence requires 8 machine cycles (2

µs @16 MHz) after the

completion of the current instruction. The interrupt service task terminates upon execution of an interrupt return

instruction [RETI] (for maskable interrupts) or [RETN] (for non-maskable interrupts). Figure 3-1 shows the timing

chart of interrupt acceptance processing.

3.3.1 Interrupt acceptance processing is packaged as follows.

a. The interrupt master enable flag (IMF) is cleared to “0” in order to disable the acceptance of any fol-

lowing interrupt.

b. The interrupt latch (IL) for the interrupt source accepted is cleared to “0”.

c. The contents of the program counter (PC) and the program status word, including the interrupt master

enable flag (IMF), are saved (Pushed) on the stack in sequence of PSW + IMF, PCH, PCL. Mean-

while, the stack pointer (SP) is decremented by 3.

d. The entry address (Interrupt vector) of the corresponding interrupt service program, loaded on the vec-

tor table, is transferred to the program counter.

e. The instruction stored at the entry address of the interrupt service program is executed.

Note:When the contents of PSW are saved on the stack, the contents of IMF are also saved.

Note 1: a: Return address entry address, b: Entry address, c: Address which RETI instruction is stored

Note 2: On condition that interrupt is enabled, it takes 38/fc [s] or 38/fs [s] at maximum (If the interrupt latch is set at the first

machine cycle on 10 cycle instruction) to start interrupt acceptance processing since its interrupt latch is set.

Figure 3-1 Timing Chart of Interrupt Acceptance/Return Interrupt Instruction

Example: Correspondence between vector table address for INTTBT and the entry address of the interrupt

service program

Figure 3-2 Vector table address,Entry address

c + 1

Execute

instruction

Execute

instruction

− 2

n - 3

− 2n − 1

− 1

a + 2

a + 1

c + 2

b + 3

b + 2

b + 1

a + 1

− 1

Execute RETI instruction

Interrupt acceptance

Execute

instruction

Interrupt service task

1-machine cycle

Interrupt

request

Interrupt

latch (IL)

IMF

D2H

03H

D203H

D204H

06H

Vector table address

Entry address

0FH

Vector

Interrupt

service

program

FFF0H

FFF1H

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