HMS87C1808B Datasheet, PDF (48/99 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

HMS87C1X04B/08B/16B
12. TIMER / COUNTER
The HMS87C1X04B/08B/16B has four Timer/Counter registers.
Each module can generate an interrupt to indicate that an event
has occurred (i.e. timer match).
Timer 0 and Timer 1 can be used either the two 8-bit Timer/Coun-
ter or one 16-bit Timer/Counter by combining them. Also Timer
2 and Timer 3 are same. In this document, explain Timer 0 and
Timer 1 because Timer2 and Timer3 same with Timer 0 and Tim-
er 1.
In the “timer” function, the register is increased every internal
clock input. Thus, one can think of it as counting internal clock
input. Since the least clock consists of 2 and the most clock con-
sists of 2048 oscillator periods, the count rate is 1/2 to 1/2048 of
the oscillator frequency in Timer0. And Timer1 can use the same
clock source too. In addition, Timer1 has more fast clock source
(1/1 to 1/8).
In the “counter” function, the register is increased in response to
a 0-to-1 (rising edge) transition at its corresponding external input
pin, EC0(Timer 0) or EC1(Timer 2).
Note: In the external event counter function, the RA0/EC0
pin has not a schmitt trigger, but a normal input port. There-
fore, it may be count more than input event signal if the
noise interfere in slow transition input signal .
In addition the “capture” function, the register is increased in re-
sponse external interrupt same with timer function. When exter-
nal interrupt edge input, the count register is captured into capture
data register CDRx.
Timer1 and Timer 3 are shared with “PWM” function and “Com-
pare output” function
It has seven operating modes: “8-bit timer/counter”, “16-bit tim-
er/counter”, “8-bit capture”, “16-bit capture”, “8-bit compare
output”, “16-bit compare output” and “10-bit PWM” which are
selected by bit in Timer mode register TMx as shown in Figure
12-1 and Table 12-1 .
Timer 0(2) Mode Register
TM0(2)
-
-
CAPx TxCK2 TxCK1 TxCK0 TxCN TxST
ADDRESS : D0H (D6H for TM2)
RESET VALUE : --00_0000
CAP0
CAP2
T0CK[2:0]
T2CK[2:0]
Capture mode selection bit.
0 : Disables Capture
1 : Enables Capture
Input clock selection
000 : fxin ÷ 2, 100 : fxin ÷ 128
001 : fxin ÷ 4, 101 : fxin ÷ 512
010 : fxin ÷ 8, 110 : fxin ÷ 2048
011 : fxin ÷ 32, 111 : External Event ( EC0(1) )
T0CN
T2CN
T0ST
T2ST
Continue control bit
0 : Stop counting
1 : Start counting continuously
Start control bit
0 : Stop counting
1 : Counter register is cleared and start again
Timer 1(3) Mode Register
TM1(3)
POL
16BIT PWMxE CAPx TxCK1 TxCK0 TxCN
TxST
ADDRESS : D2H (D8H for TM3)
RESET VALUE : 0000_0000
POL
16BIT
PWM0E
PWM1E
CAP1
CAP3
PWM Output Polarity
0 : Duty active low
1 : Duty active high
16-bit mode selection
0 : 8-bit mode
1 : 16-bit mode
PWM enable bit
0 : Disables PWM
1 : Enables PWM
Capture mode selection bit.
0 : Disables Capture
1 : Enables Capture
T1CK[2:0]
T3CK[2:0]
T1CN
T3CN
T1ST
T3ST
Input clock selection
00 : fxin
10 : fxin ÷ 8
01 : fxin ÷ 2 11 : using the Timer 0 clock
Continue control bit
0 : Stop counting
1 : Start counting continuously
Start control bit
0 : Stop counting
1 : Counter register is cleared and start again
Figure 12-1 Timer Mode Register (TMx, x = 0~3)
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SEP. 2004 Ver 1.03