M16CSLASH1N datasheet(221/238 Pages) RENESAS

221 / 238 page

Rev.1.00

Oct 20, 2004

page 209 of 222

M16C/1N Group

REJ090007-0100Z

20. Precautionary Notes in Using the Device

20.3 Timer

20.3.1 Timer 1

1. Even if the prescaler 1 and Timer 1 are read out simultaneously in word-size, these registers are

read byte-by-byte in the microcomputer. Consequently, the timer value may be updated during the

period these two registers are being read.

20.3.2 Timers X, Y and Z

1. These timers stop counting after reset. Therefore, set values to Timer (X, Y, Z) and prescaler (X, Y,

Z) before starting counting.

2. Even if prescaler (X, Y, Z) and Timer (X, Y, Z) are read out simultaneously in word-size, these

registers are read byte-by-byte in the microcomputer. Consequently, the timer value may be up-

dated during the period these two registers are being read.

20.3.3 Timer X

1. Using in the timer X pulse period measurement mode, the effectual edge reception flag and the

timer X under flow flag are set to "0" by writing a "0" in a program. Writing a "1" has no effect. Write

"1" in the other flag by using the MOV instruction when you make the flag of either one side "0" by

program. (The clearance of the flag which isn't intend can be prevented.)

Example:

MOV.B

#10XXXXXXB,008BH

2. When changing to the timer X pulse period measurement mode from other mode, the contents of

the effectual edge reception flag and the timer X under flow flag are indetermind. Write "0" in the

effectual edge reception flag and the timer X under flow flag before starting the timer.

3. In the timer X pulse period measurement mode, use the MOV instruction to stop the timer.

Example:

MOV.B

#1100X00B,008BH

20.3.4 Timer Y

1. When count is stopped by writing "0" to the timer Y count start flag, the timer reloads the value of

reload register and stops. Therefore, the timer count value should be read out before the timer

stops.

2. When count is stopped by writing "0" to the timer Y count start flag, the timer Y interrupt request bit

becomes "1" and an interrupt may occur. Thus, disable interrupts before the timer stops. Further-

more, set the Timer Y interrupt request bit to "0" before starting counting again.

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