H838532H datasheet(102/508 Pages) RENESAS

102 / 508 page

Section 3 Exception Handling

Rev. 1.00 May 30, 2008 Page 82 of 484

REJ09B0436-0100

Figure 3.7 shows the procedure for setting a bit in a port mode register and clearing the interrupt

request flag.

When switching a pin function, mask the interrupt before setting the bit in the port mode register.

After accessing the port mode register, execute at least one instruction (e.g., NOP), then clear the

interrupt request flag from 1 to 0. If the instruction to clear the flag is executed immediately after

the port mode register access without executing an intervening instruction, the flag will not be

cleared.

An alternative method is to avoid the setting of interrupt request flags when pin functions are

switched by keeping the pins at the high level so that the conditions in table 3.5 do not occur.

CCR I bit

Set port mode register bit

Execute NOP instruction

Interrupts masked. (Another possibility

is to disable the relevant interrupt in

interrupt enable register 1.)

After setting the port mode register bit,

first execute at least one instruction

(e.g., NOP), then clear the interrupt

request flag to 0

Interrupt mask cleared

Clear interrupt request flag to 0

←

CCR I bit

←

Figure 3.7 Port Mode Register Setting and Interrupt Request Flag Clearing Procedure

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