R8CSLASH20 datasheet(111/501 Pages) RENESAS

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R8C/20 Group, R8C/21 Group

12. Interrupts

Rev.2.00 Aug 27, 2008

Page 95 of 458

REJ09B0250-0200

12.1.6.1

I Flag

The I flag enables or disables the maskable interrupt. Setting the I flag to 1 (enabled) enables the maskable

interrupt. Setting the I flag to 0 (disabled) disables all maskable interrupts.

12.1.6.2

IR Bit

The IR bit is set to 1 (interrupt requested) when an interrupt request is generated. Then, when the interrupt

request is acknowledged and the CPU branches to the corresponding interrupt vector, the IR bit is set to 0 (=

interrupt not requested).

The IR bit can be set to 0 by a program. Do not write 1 to this bit.

Operations of the IR bit vary by Timer RD interrupt, clock synchronous serial I/O interrupt with chip select or

I2C bus interface interrupt.

For details, refer to 12.5 Timer RD Interrupt, Clock Synchronous Serial I/O with Chip Select Interrupts

and I2C bus Interface Interrupts (Interrupts with Multiple Interrupt Request Sources).

12.1.6.3

Bits ILVL2 to ILVL0 and IPL

Interrupt priority levels can be set using the ILVL2 to ILVL0 bits.

Table 12.3 lists the Settings of Interrupt Priority Levels and Table 12.4 lists the Interrupt Priority Levels

Enabled by IPL.

The following are conditions under which an interrupt is acknowledged:

• I flag = 1

• IR bit = 1

• Interrupt priority level > IPL

The I flag, IR bit, ILVL2 to ILVL0 bits and IPL are independent of each other. They do not affect one another.

Table 12.3

Settings of Interrupt Priority

Levels

ILVL2 to ILVL0 Bits

Interrupt Priority Level

Priority Order

000b

Level 0 (interrupt disabled)

−

001b

Level 1

Low

010b

Level 2

011b

Level 3

100b

Level 4

101b

Level 5

110b

Level 6

111b

Level 7

High

Table 12.4

Interrupt Priority Levels Enabled by

IPL

Enabled Interrupt Priority Levels

000b

Interrupt level 1 and above

001b

Interrupt level 2 and above

010b

Interrupt level 3 and above

011b

Interrupt level 4 and above

100b

Interrupt level 5 and above

101b

Interrupt level 6 and above

110b

Interrupt level 7 and above

111b

All maskable interrupts are disabled

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