W79E201 Datasheet, PDF (43/87 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E201
timers will increment at the rate of 1/4 clock speed. This will straight-away increase the counting
speed three times. This selection is done by the T0M and T1M bits in CKCON SFR. A reset sets these
bits to 0, and the timers then operate in the standard 8051 mode. The user should set these bits to 1 if
the timers are to operate in turbo mode.
Mode 0
In Mode 0, the timer/counters act as a 8 bit counter with a 5 bit, divide by 32 pre-scale. In this mode
we have a 13 bit timer/counter. The 13 bit counter consists of 8 bits of THx and 5 lower bits of TLx.
The upper 3 bits of TLx are ignored.
The negative edge of the clock is increments the count in the TLx register. When the fifth bit in TLx
moves from 1 to 0, then the count in the THx register is incremented. When the count in THx is
moving from FFh to 00h, then the overflow flag TFx in TCON SFR is set. The counted input is enabled
only if TRx is set and either GATE = 0 or INTx = 1. When C/T is set to 0, then it will count clock
cycles, and if C/T is set to 1, then it will count 1 to 0 transitions on T0 (P3.4) for timer 0 and T1 (P3.5)
for timer 1. When the 13 bit count reaches 1FFFh the next count will cause it to roll-over to 0000h. The
timer overflow flag TFx of the relevant timer is set and if enabled an interrupts will occur. Note that
when used as a timer, the time-base may be either clock cycles/12 or clock cycles/4 as selected by
the bits TxM of the CKCON SFR.
osc
T0M = CKCON.3
(T1M = CKCON.4)
1/4
1
0
1/12
T0 = P3.4
(T1 = P3.5)
TR0 = TCON.4
(TR1 = TCON.6)
C/T = TMOD.2
(C/T = TMOD.6)
0
1
GATE = TMOD.3
(GATE = TMOD.7)
INT0 = P3.2
(INT1 = P3.3)
Timer 1 functions are shown in brackets
M1,M0 = TMOD.1,TMOD.0
(M1,M0 = TMOD.5,TMOD.4)
00
0
4
7
0
7
TL0
(TL1)
01
TH0
(TH1)
TFx
TF0
(TF1)
Interrupt
Timer/Counter Mode 0 & Mode 1
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Publication Release Date: December 16, 2004
Revision A2