TMP93CS40 datasheet(49/248 Pages) TOSHIBA

49 / 248 page

TMP93CS40/TMP93CS41

2004-02-10

93CS40-47

3.4.3

Interrupt Controller

Figure 3.4.4 is a block diagram of the interrupt circuits. The left half of the diagram

shows the interrupt controller; the right half includes the CPU interrupt request signal

circuit and the halt release signal circuit.

Each interrupt channel (Total of 20 channels) in the interrupt controller has an interrupt

request flag, interrupt priority setting register, and a register for storing the micro DMA

start vector. The interrupt request flag is used to latch interrupt requests from peripheral

devices.

The flag is cleared to 0 when any of the following conditions are met.

•

Upon resetting

•

When the CPU reads the interrupt vector after acceptance of an interrupt.

•

When the CPU executes an instruction that clears the interrupt from that channel

(Writes 0 in <IxxC> of the interrupt priority setting register).

For example, to clear the INT0 interrupt request, after the DI instruction set the register

INTE0AD as follows.

INTE0AD

← − − − − 0 − − −

Clears the INT0 flip-flop.

The status of the interrupt request flag is detected by reading the corresponding clear bit.

This also allows the interrupt to be identified by the software.

The interrupt priority can be set by writing the priority in the interrupt priority setting

levels to be set range from or 1 to 6. Except for NMIs (Non-maskable interrupts), writing 0

or 7 as the interrupt priority disables the corresponding interrupt request. The priority of

non-maskable interrupt sources ( NMI pin, watchdog timer, etc.) is fixed to 7. If interrupt

requests with the same interrupt level are generated simultaneously, interrupts are

accepted in accordance with the default ranking of priorities.

The interrupt controller selects the interrupt request with the highest priority among the

simultaneous interrupts, and sends it and its vector address to the CPU. The CPU

compares the priority value <IFF2:0> set in the status register, with the priority value sent

by the interrupt request signal; if the latter is higher, the interrupt is accepted. Then the

CPU sets in CPU SR<IFF2:0> a value equal to one plus the priority value of the interrupt

request just received. Interrupt requests whose priority values equal or are higher than the

value set in the register are accepted concurrently with execution of the previous interrupt

routine. When interrupt processing is completed (after execution of the RETI instruction),

the CPU restores to CPU SR<IFF2:0> the priority value saved in the stack before the

interrupt was generated.

The interrupt controller also has four registers used to store the micro DMA start vector.

Unlike other micro DMA registers (DMAS, DMAD, DMAM, and DMAC), these are I/O

registers. Writing the start vector of the interrupt source for micro DMA processing (See

Table 3.4.1), enables the corresponding interrupt to be processed by micro DMA. Please

note that appropriate values must be set in the micro DMA parameter registers (e.g.,

DMAS and DMAD) prior to the beginning of micro DMA processing.

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