R8C-24_1 Datasheet, PDF (304/525 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MCU R8C FAMILY / R8C/2x SERIES

R8C/24 Group, R8C/25 Group
14. Timers
14.4.3.3 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
register is set to 1 (timer RE interrupt request generated).
• 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.
Rev.3.00 Feb 29, 2008 Page 287 of 485
REJ09B0244-0300