M16C80 Datasheet, PDF (219/358 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/80 SERIES

M16C/80 Group
27. Usage Precaution
27. Usage Precaution
SFR (100-pin version)
(1) Addresses 03C916, 03CB16 to 03D316 , 03DC16 area is for future plan. Must set "FF16" to address
03CB16, 03CE16, 03CF16, 03D216, 03D316 and "0016" to address 03DC16 at initial setting.
Timer
(1) A timer Ai register and a timer Bi register are unstable after MCU resetting. Please start a count
after setting a value as the timer Ai register or timer Bi register to be used, when using a timer.
Timer A (timer mode)
(1) Reading the timer Ai register while a count is in progress allows reading, with arbitrary timing, the
value of the counter. Reading the timer Ai register with the reload timing gets “FFFF16”. Reading
the timer Ai register after setting a value in the timer Ai register with a count halted but before the
counter starts counting gets a proper value.
Timer A (event counter mode)
(1) Reading the timer Ai register while a count is in progress allows reading, with arbitrary timing, the
value of the counter. Reading the timer Ai register with the reload timing gets “FFFF16” by under-
flow or “000016” by overflow. Reading the timer Ai register after setting a value in the timer Ai
register with a count halted but before the counter starts counting gets a proper value.
(2) When stop counting in free run type, set timer again.
(3) In the case of using as “Free-Run type”, the timer register contents may be unknown when count-
ing begins. If the timer register is set before counting has started, then the starting value will be
unknown.
• In the case where the up/down count will not be changed.
Enable the “Reload” function and write to the timer register before counting begins. Re-
write the value to the timer register immediately after counting has started. If counting
up, rewrite “000016” to the timer register. If counting down, rewrite “FFFF16” to the timer
register. This will cause the same operation as “Free-Run type” mode.
• In the case where the up/down count has changed.
First set to “Reload type” operation. Once the first counting pulse has occurred, the timer
may be changed to “Free-Run type”.
Rev.1.00 Aug. 02, 2005 ^{Page 208} of 329
REJ09B0187-0100