7906 datasheet(347/531 Pages) RENESAS

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STOP AND WAIT MODES

7906 Group User’s Manual Rev.2.0

15-6

15.2 Block description

15.2.2 Particular function select register 1

Figure 15.2.4 shows the structure of the particular function select register 1.

Notes 1: At power-on rest, this bit becomes “0.” At hardware reset or software reset, this bit retains the value just before reset.

2: Even when “1” is written, the bit status will not change.

3: Setting this bit to “1” must be performed just before execution of the WIT instruction. Also, after the wait state is terminated,

this bit must be cleared to “0” immediately.

(Note 1)

Bit name

Bit

Particular function select register 1 (Address 6316)

Function

At reset

R/W

STP-instruction-execution status

bit

WIT-instruction-execution status

bit

Fix this bit to “0”.

System clock stop select bit at

WIT

(Note 3)

Fix this bit to “0”.

The value is “0” at reading.

Timer B2 clock source select bit

(Valid in event counter mode)

The value is “0” at reading.

b7 b6 b5 b4 b3 b2 b1 b0

0 : Normal operation.

1 : STP instruction has been executed.

0 : Normal operation.

1 : WIT instruction has been executed.

0 : In wait mode, system clock fsys is active.

1 : In wait mode, system clock fsys is stopped.

0 : External signal input to the TB2IN pin is counted.

1 : fX32 is counted.

(Note 2)

—

Fig. 15.2.4 Structure of particular function select register 1

(1) STP-instruction-execution status bit (bit 0)

When the microcomputer enters the stop mode, this bit becomes “1,” indicating that the STP instruction

has been executed.

This bit becomes “0” at power-on reset. At hardware reset and software reset, this bit retains the value

immediately before reset. Therefore, this bit is used for the following verification:

• Which of the power-on reset and hardware reset has been used to reset the system?

• Has the hardware reset been used for the stop mode termination?

This bit is cleared to “0” by writing “0” to this bit. Although, even when “1” is written to this bit, this

bit does not change.

At the stop mode termination, be sure to clear this bit to “0” by software.

(2) WIT-instruction-execution status bit (bit 1)

When the microcomputer enters the wait mode, this bit becomes “1,” indicating that the WIT instruction

has been executed.

This bit becomes “0” at power-on reset. At hardware reset and software reset, this bit retains the value

immediately before reset. Therefore, this bit is used for the following verification:

• Which of the power-on reset and hardware reset has been used to reset the system?

• Has the hardware reset been used for the wait mode termination?

This bit is cleared to “0” by writing “0” to this bit. Although, even when “1” is written to this bit, this

bit does not change.

At the wait mode termination, be sure to clear this bit to “0” by software.

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