R8C2K datasheet(450/471 Pages) RENESAS

450 / 471 page

R8C/2K Group, R8C/2L Group

23. Usage Notes

Rev.1.10

Dec 21, 2007

Page 433 of 450

REJ09B0406-0110

23.3.4

Notes on Timer RD

23.3.4.1

TRDSTR Register

• Set the TRDSTR register using the MOV instruction.

• When the CSELi (i = 0 to 1) is set to 0 (the count stops at compare match of registers TRDi and TRDGRAi),

the count does not stop and the TSTARTi bit remains unchanged even if 0 (count stops) is written to the

TSTARTi bit.

• Therefore, set the TSTARTi bit to 0 to change other bits without changing the TSTARTi bit when the CSELi

bit is se to 0.

• To stop counting by a program, set the TSTARTi bit after setting the CSELi bit to 1. Although the CSELi bit is

set to 1 and the TSTARTi bit is set to 0 at the same time (with 1 instruction), the count cannot be stopped.

• Table 23.1 lists the TRDIOji (j = A, B, C, or D) Pin Output Level when Count Stops to use the TRDIOji (j =

A, B, C, or D) pin with the timer RD output.

23.3.4.2

TRDi Register (i = 0 or 1)

• When writing the value to the TRDi register by a program while the TSTARTi bit in the TRDSTR register is

set to 1 (count starts), avoid overlapping with the timing for setting the TRDi register to 0000h, and then write.

If the timing for setting the TRDi register to 0000h overlaps with the timing for writing the value to the TRDi

These precautions are applicable when selecting the following by bits CCLR2 to CCLR0 in the TRDCRi

- 001b (Clear by the TRDi register at compare match with the TRDGRAi register.)

- 010b (Clear by the TRDi register at compare match with the TRDGRBi register.)

- 011b (Synchronous clear)

- 101b (Clear by the TRDi register at compare match with the TRDGRCi register.)

- 110b (Clear by the TRDi register at compare match with the TRDGRDi register.)

• When writing the value to the TRDi register and continuously reading the same register, the value before

writing may be read. In this case, execute the JMP.B instruction between the writing and reading.

Program example

MOV.W

#XXXXh, TRD0

;Writing

JMP.B

;JMP.B

L1:

MOV.W

TRD0,DATA

;Reading

23.3.4.3

TRDSRi Register (i = 0 or 1)

When writing the value to the TRDSRi register and continuously reading the same register, the value before

writing may be read. In this case, execute the JMP.B instruction between the writing and reading.

Program example

MOV.B

#XXh, TRDSR0

;Writing

JMP.B

;JMP.B

L1:

MOV.B

TRDSR0,DATA

;Reading

Table 23.1

TRDIOji (j = A, B, C, or D) Pin Output Level when Count Stops

Count Stop

TRDIOji Pin Output when Count Stops

When the CSELi bit is set to 1, set the TSTARTi bit to 0 and the count

stops.

Hold the output level immediately before the

count stops.

When the CSELi bit is set to 0, the count stops at compare match of

registers TRDi and TRDGRAi.

Hold the output level after output changes by

compare match.

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