W77C58 Datasheet, PDF (50/71 Pages) Winbond – 8 BIT MICROCONTROLLER

Preliminary W77C58
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. The modes available on Timer 2 are
described below.
Mode
RCLK+TCLK CP/RL2
T2OE
Auto-reload mode
0
0
0
Capture Mode
0
1
X
Baud rate generator
1
X
0
Programmable clock out
X
0
1
Capture Mode
The capture mode is enabled by setting the CP/RL2 bit in the T2CON register to a 1. In the capture
mode, Timer/Counter 2 serves as a 16 bit up counter. When the counter rolls over from FFFFh to
0000h, the TF2 bit is set, which will generate an interrupt request. If the EXEN2 bit is set, then a
negative transition of T2EX pin will cause the value in the TL2 and TH2 register to be captured by the
RCAP2L and RCAP2H registers. This action also causes the EXF2 bit in T2CON to be set, which will
also generate an interrupt. Setting the T2CR bit (T2MOD.3), the W77C58 allows hardware to reset
timer 2 automatically after the value of TL2 and TH2 have been captured.
Clock Source
Mode
input
div. by 4
osc/1
div. by 64 osc/16
div. by 1024 osc/256
T2 = P1.0
TR2 = T2CON.2
T2EX = P1.1
EXEN2 = T2CON.3
T2M = CKCON.5
1/4
1
C/T2 = T2CON.1
0
1/12
0
1
TL2 TH2
T2CON.7
TF2
RCAP2L RCAP2H
L
HH
EXF2
T2CON.6
Figure 14. 16-Bit Capture Mode
Timer 2
Interrupt
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