SM5958
8-Bit Micro-controller
32KB with ISP Flash
& 1KB RAM embedded
FFH
FFH
EXF2
Fosc/12
C/T2=0
C/T2=1
TL2
TH2
TF2
T2 pin
Timer2
interrupt
TR2
RCAP2L
RCAP2H
Count Direction
1 = UP
0 = DOWN
T2EX PIN
Timier2 in Auto Reload Mode
(DCEN=1)
Fig. 7-3： Timer 2 in auto reload mode (DCEN=1)
7.3
Programmable clock out
A 50% duty cycle clock can be programmed to come out on P1.0. This pin, besides begin a regular I/O pin, has two
alternate functions. It can be programmed (1) to input the external clock for Timer/Counter 2 or (2) to output a 50%
duty cycle clock. An example is that the clock output ranges from 61Hz to 4MHz at a 16MHz oscillator frequency if
in 12T mode.
To configure the Timer/Counter 2 as a clock generator, bit C/
T
2
(T2CON.1) must be cleared and bit
T2OE(T2MOD.1) must be set. Bit TR2 (T2CON.2) starts and stops the timer.
The Clock-Out frequency depends on the oscillator frequency and the reload value of Timer 2 capture registers
(RCAP2H, RCAP2L) as shown in this equation:
Clock-Out Frequency =
Oscillator Frequency
4
×
(65536
−
RCAP
2
H
,
RCAP
2
L
)
In the clock-out mode, Timer 2 roll-overs will not generate an interrupt. This is similar to when Timer 2 is used as a
baud-rate generator. It is possible to use Timer 2 as a baud-rate generator and a clock generator simultaneously.
Note, however, that the baud-rate and clock-out frequencies can not be determined independently from one
another since they both use RCAP2H and RCAP2L.
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M089
Ver A SM5958 3/19/2014
- 32 -
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
