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5.3

5.3.1

Interrupt Priority Registers A–E (IPRA–IPRE)

The five registers from IPRA–IPRE are 16-bit read/write registers that assign priority levels from

0–15 to the IRQ and on-chip peripheral module interrupt sources. Interrupt request sources are

mapped onto IPRA–IPRE as shown in table 5.4.

Bit:

Bit name:

Initial value:

R/W:

R/W

Bit:

Bit name:

Initial value:

R/W:

R/W

Table 5.4

Interrupt Request Sources and IPRA–IPRE

Bits 15–12

Bits 11–8

Bits 7–4

Bits 3–0

IPRA

IRQ0

IRQ1

IRQ2

IRQ3

IPRB

IRQ4

IRQ5

IRQ6

IRQ7

IPRC

DMAC0, DMAC1

DMAC2, DMAC3

ITU0

ITU1

IPRD

ITU2

ITU3

ITU4

SCI0

IPRE

SCI1

PRT*1

WDT, REF*2

(Reserved)*3

Notes: 1. PRT: Parity control unit of bus state controller. See section 8, Bus State Controller, for

details.

2. REF: DRAM refresh control unit of bus controller. See section 8, Bus State Controller,

for details.

3. When read, always 0. Always write 0 in reserved bits.

As indicated in table 5.4, four

IRQ pins or four groups of on-chip peripheral modules are assigned

to each interrupt priority register. The priority levels for the four pins or groups can be set by

setting the corresponding 4-bit groups of bits 15–12, bits 11–8, bits 7–4, and bits 3–0 (of IPRA–

IPRE) with values in the range of H'0 (0000) to H'F (1111). Setting H'0 gives interrupt priority

level 0 (the lowest). Setting H'F gives level 15 (the highest). When two on-chip peripheral

modules are assigned to the same bits (DMAC0 and DMAC1, or DMAC2 and DMAC3, or the

watchdog timer and DRAM refresh control unit), those two modules have the same priority. A

reset initializes IPRA–IPRE to H'0000. They are not initialized by the standby mode.

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