LAPIS Semiconductor ML610421, User Manual, Page: 157 / 437

ML610Q421/ML610Q422/ML610421 User’s Manual
Chapter 10 Timers
10 – 22
(4) Set “FFH” to both TM2D register and TM3D register.
(5) Clear both TM2C register and TM3C register to “00H”.
(6) Set T2RUN bit (bit0 of TM2CON1 register) to “1” to start counting the timer.
(7) On the condition of (T23MFM
ビット
=="1") & ((TM23M16
ビット
=="1") & (T2RUN
ビット
=="1"), the
count-up starts at rising edge of 64Hz clock signal.
(8) The count-up stops at the falling edge of the next timer clock (HTBCLK) after 437C signal becomes “1”.
Also, at the same time, T2RUN bit and T2STAT bit become “0” and the interrupt signal TM3INT activates.
(9) After checking T2STAT bit or TM3INT interrupt occurs, read out the data (N1) of TM2C register and TM3C
register.
For example of utilizing N1, to occur 9600Hz timer interrupt.
Assuming the HTBCLK is 600kHz,
N1 = 600000 * 437 / 32768
= 8001 (Decimal)
= 1F41 (Hexadecimal)
= 0001 1111 0100 0001 (Binary)
As (437 / 32768) sec is equivalent to 128 clocks at 9600Hz (more precisely, 9598Hz), a division of the count N1
by 128 equals frequency ratio (N2) between the frequency of HTBCLK and 9600Hz.
Because 128 = 2
7
, that caluculation can be determined by truncating the righthand seven digits of N1(Binary).
N2 = 8001(Decimal) / 128 (Decimal)
=0001 1111 0 (Binary)
=3E (Hexadecimal)
=62 (Decimal)
This indicates that 9600Hz is about 62 times the cycle of HTBCLK.
Therefore, if 3DH(=3EH-1) set to the timer register and the timer start counting, the cycle of TMnINT interrupt
that can occur every 62 counts of HTBCLK is:
tTMnINT = (1 / 600000) * 62 = 0.10333ms (9677Hz)