HMS99C52 Datasheet, PDF (22/43 Pages) Hynix Semiconductor – 8-BIT SINGLE-CHIP MICROCONTROLLERS

HMS99C5X Series
TIMER / COUNTER 0 AND 1
Timer/Counter 0 and 1 can be used in four operating modes as listed in Table 4:
Table 4. Timer/Counter 0 and 1 Operating Modes
Mode
0
1
2
3
Description
Gate
TMOD
C/T M1
8-bit timer/counter with a
divide-by-32 prescaler
X
X
0
16-bit timer/counter
X
X
0
8-bit timer/counter with
8-bit auto-reload
X
X
1
Timer/counter 0 used as
X
X
1
one 8-bit timer/counter and
one 8-bit timer Timer 1
stops
Input Clock
M0
internal
external (Max.)
0 f_OSC ÷(12×32) f_OSC ÷(24×32)
1
f_OSC ÷12
0
f_OSC ÷12
f_OSC ÷24
f_OSC ÷24
1
f_OSC ÷12
f_OSC ÷24
In the "timer" function (C/T = "0") the register is incremented every machine cycle. Therefore the count rate is
f_OSC/12.
In the "counter" function the register is incremented in response to a 1-to-0 transition at its corresponding exter-
nal input pin (P3.4/T0, P3.5/T1). Since it takes two machine cycles to detect a falling edge the max. count rate
is f_OSC/24. External inputs INT0 and INT1 (P3.2, P3.3) can be programmed to function as a gate to facilitate
pulse width measurements. Figure 4 illustrates the input clock logic.
fOSC
÷ 12
P3.4/T0
P3.5/T1
Max. f_OSC/24
TR0 / 1
TCON
Gate
=1
TMOD
P3.2 / INT0
P3.3 / INT1
C/T
TMOD
0
1
&
≥1
Figure 4. Timer/Counter 0 and 1 Input Clock Logic
18
fOSC ÷ 12
Timer 0/1
Input Clock
Jan. 2003 Ver 1.0