W79E648 Datasheet, PDF (40/80 Pages) Winbond – Fast 8051 Compatible microcontroller with a redesigned Processor

Preliminary W79E648
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
T0 = P3.4
(T1 = P3.5)
TR0 = TCON.4
(TR1 = TCON.6)
T0M = CKCON.3
(T1M = CKCON.4)
1/4
1
1/12
0
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
TL0
(TL1)
0
7
01
TH0
(TH1)
TFx
TF0
(TF1)
Interrupt
Figure 11. Timer/Counter Mode 0 & Mode 1
Mode 1
Mode 1 is similar to Mode 0 except that the counting register forms a 16 bit counter, rather than a 13
bit counter. This means that all the bits of THx and TLx are used. Roll-over occurs when the timer
moves from a count of FFFFh to 0000h. The timer overflow flag TFx of the relevant timer is set and if
enabled an interrupt will occur. The selection of the time-base in the timer mode is similar to that in
Mode 0. The gate function operates similarly to that in Mode 0.
Mode 2
In Mode 2, the timer/counter is in the Auto Reload Mode. In this mode, TLx acts as a 8 bit count
register, while THx holds the reload value. When the TLx register overflows from FFh to 00h, the TFx
bit in TCON is set and TLx is reloaded with the contents of THx, and the counting process continues
from here. The reload operation leaves the contents of the THx register unchanged. Counting is
enabled by the TRx bit and proper setting of GATE and INTx pins. As in the other two modes 0 and 1
mode 2 allows counting of either clock cycles (clock/12 or clock/4) or pulses on pin Tn.
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