w77e58 Winbond Electronics Corp America, w77e58 Datasheet - Page 56

• Manufacturer Part Number: w77e58
• Description: 8 Bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

MODE 3
Mode 3 has different operating methods for the two timer/counters. For timer/counter 1, mode 3
simply freezes the counter. Timer/Counter 0, however, configures TL0 and TH0 as two separate 8 bit
count registers in this mode. The logic for this mode is shown in the figure. TL0 uses the
Timer/Counter 0 control bits C T
cycles (clock/12 or clock/4) or 1-to-0 transitions on pin T0 as determined by C/T (TMOD.2). TH0 is
forced as a clock cycle counter (clock/12 or clock/4) and takes over the use of TR1 and TF1 from
Timer/Counter 1. Mode 3 is used in cases where an extra 8 bit timer is needed. With Timer 0 in Mode
3, Timer 1 can still be used in Modes 0, 1 and 2., but its flexibility is somewhat limited. While its basic
functionality is maintained, it no longer has control over its overflow flag TF1 and the enable bit TR1.
Timer 1 can still be used as a timer/counter and retains the use of GATE and INT1 pin. In this
condition it can be turned on and off by switching it out of and into its own Mode 3. It can also be used
as a baud rate generator for the serial port.
TIMER/COUNTER 2
Timer/Counter 2 is a 16 bit up/down counter which is configured by the T2MOD register and
controlled by the T2CON register. Timer/Counter 2 is equipped with a capture/reload capability. As
with the Timer 0 and Timer 1 counters, there exists considerable flexibility in selecting and controlling
the clock, and in defining the operating mode. The clock source for Timer/Counter 2 may be selected
for either the external T2 pin (C/T2 = 1) or the crystal oscillator, which is divided by 12 or 4 (C/T2 =
0). The clock is then enabled when TR2 is a 1, and disabled when TR2 is a 0.
div. by 4
div. by 64
div. by 1024 osc/256
Mode
Clock Source
(GATE = TMOD.7)
GATE = TMOD.3
(TR1 = TCON.6)
TR0 = TCON.4
(INT1 = P3.3)
INT0 = P3.2
(T1 = P3.5)
T0 = P3.4
osc/1
osc/16
input
1/12
(T1M = CKCON.4)
1/4
T0M = CKCON.3
1
0
/
, GATE, TR0, INT0 and TF0. The TL0 can be used to count clock
0
1
(C/T = TMOD.6)
C/T = TMOD.2
Figure 12. Timer/Counter Mode 2.
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0
Timer 1 functions are shown in brackets
0
(TH1)
(TL1)
TH0
TL0
Preliminary W77E58
7
7
TFx
(TF1)
TF0
Interrupt