R8CSLASH2G datasheet(326/344 Pages) RENESAS

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R8C/2G Group

23. Usage Notes

Rev.1.00

Apr 04, 2008

Page 306 of 318

REJ09B0387-0100

23.6.3.3

Time Reading Procedure of Real-Time Clock Mode

In real-time clock mode, read registers TRESEC, TREMIN, TREHR, and TREWK when time data is updated

and read the PM bit in the TRECR1 register when the BSY bit is set to 0 (not while data is updated).

Also, when reading several registers, an incorrect time will be read if data is updated before another register is

read after reading any register.

In order to prevent this, use the reading procedure shown below.

• Using an interrupt

Read necessary contents of registers TRESEC, TREMIN, TREHR, and TREWK and the PM bit in the

TRECR1 register in the timer RE interrupt routine.

• Monitoring with a program 1

Monitor the IR bit in the TREIC register with a program and read necessary contents of registers TRESEC,

TREMIN, TREHR, and TREWK and the PM bit in the TRECR1 register after the IR bit in the TREIC

• Monitoring with a program 2

(1) Monitor the BSY bit.

(2) Monitor until the BSY bit is set to 0 after the BSY bit is set to 1 (approximately 62.5 ms while the BSY

bit is set to 1).

(3) Read necessary contents of registers TRESEC, TREMIN, TREHR, and TREWK and the PM bit in the

TRECR1 register after the BSY bit is set to 0.

• Using read results if they are the same value twice

(1) Read necessary contents of registers TRESEC, TREMIN, TREHR, and TREWK and the PM bit in the

TRECR1 register.

(2) Read the same register as (1) and compare the contents.

(3) Recognize as the correct value if the contents match. If the contents do not match, repeat until the read

contents match with the previous contents.

Also, when reading several registers, read them as continuously as possible.

R8C/2G 数据表(PDF) 326 Page - Renesas Technology Corp