HYUNDAI MicroElectronics
GMS81C2012/GMS81C2020
12.3 8-bit Compare Output (16-bit)
The GMS81C20xx has a function of Timer Compare Out-
put. To pulse out, the timer match can goes to port
pin(T0O, T1O) as shown in Figure 12-2 and Figure 12-7.
Thus, pulse out is generated by the timer match. These op-
eration is implemented to pin, T0O, PWM1O/T1O.
tion, 16-bit Compare output mode is available, also.
This pin output the signal having a 50 : 50 duty square
wave, and output frequency is same as below equation.
Oscillation Frequency
2 × Prescaler Value × (TDR + 1)
---------------------------------------------------------------------------------
=
f
COMP
In this mode, the bit PWM1O/T1O of R5 function register
(R5FUNC.6) should be set to "1", and the bit PWM1E of
timer1 mode register (TM1) should be set to "0". In addi-
12.4 8-bit Capture Mode
The Timer 0 capture mode is set by bit CAP0 of timer
mode register TM0 (bit CAP1 of timer mode register TM1
for Timer 1) as shown in Figure 12-8.
tained correct value by counting the number of timer over-
flow occurrence.
Timer/Counter still does the above, but with the added fea-
ture that a edge transition at external input INTx pin causes
the current value in the Timer x register (T0,T1), to be cap-
tured into registers CDRx (CDR0, CDR1), respectively.
After captured, Timer x register is cleared and restarts by
hardware.
As mentioned above, not only Timer 0 but Timer 1 can also
be used as a capture mode.
The Timer/Counter register is increased in response inter-
nal or external input. This counting function is same with
normal timer mode, and Timer interrupt is generated when
timer register T0 (T1) increases and matches TDR0
(TDR1).
Note: The CDRx, TDRx and Tx are in same address. In
the capture mode, reading operation is read the CDRx, not
Tx because path is opened to the CDRx, and TDRx is only
for writing operation.
This timer interrupt in capture mode is very useful when
the pulse width of captured signal is more wider than the
maximum period of Timer.
It has three transition modes: "falling edge", "rising edge",
"both edge" which are selected by interrupt edge selection
register IEDS (Refer to External interrupt section). In ad-
dition, the transition at INTx pin generate an interrupt.
For example, in Figure 12-10, the pulse width of captured
signal is wider than the timer data value (FFH) over 2
times. When external interrupt is occurred, the captured
value (13H) is more little than wanted value. It can be ob-
MAR. 2000 Ver 1.00
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