W77C58 Datasheet, PDF (51/71 Pages) Winbond – 8 BIT MICROCONTROLLER

Preliminary W77C58
Auto-reload Mode, Counting Up
The auto-reload mode as an up counter is enabled by clearing the CP/RL2 bit in the T2CON register
and clearing the DCEN bit in T2MOD register. In this mode, Timer/Counter 2 is a 16 bit up counter.
When the counter rolls over from FFFFh, a reload is generated that causes the contents of the
RCAP2L and RCAP2H registers to be reloaded into the TL2 and TH2 registers. The reload action also
sets the TF2 bit. If the EXEN2 bit is set, then a negative transition of T2EX pin will also cause a
reload. This action also sets the EXF2 bit in T2CON.
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
T2M = CKCON.5
1/4
1 _{C/T2 = T2CON.1}
0
1/12 0
1
TL2 TH2
T2CON.7
TF2
RCAP2L RCAP2H
L
Timer 2
Interrupt
EXEN2 = T2CON.3
EXF2
T2CON.6
Figure 15. 16-Bit Auto-reload Mode, Counting Up
Auto-reload Mode, Counting Up/Down
Timer/Counter 2 will be in auto-reload mode as an up/down counter if CP/RL2 bit in T2CON is
cleared and the DCEN bit in T2MOD is set. In this mode, Timer/Counter 2 is an up/down counter
whose direction is controlled by the T2EX pin. A 1 on this pin cause the counter to count up. An
overflow while counting up will cause the counter to be reloaded with the contents of the capture
registers. The next down count following the case where the contents of Timer/Counter equal the
capture registers will load an FFFFh into Timer/Counter 2. In either event a reload will set the TF2 bit.
A reload will also toggle the EXF2 bit. However, the EXF2 bit can not generate an interrupt while in
this mode.
Clock Source
Mode input
div. by 4 osc/1
div. by 64 osc/16
div. by 1024 osc/256
1/4
1/12
T2 = P1.0
TR2 = T2CON.2
T2M = CKCON.5
1 ^{C/T = T2CON.1}
0
0
1
Down Counting Reload Value
0FFh 0FFh
TL2 TH2
T2CON.7
Timer 2
TF2
Interrupt
T2EX = P1.1
RCAP2L RCAP2H
Up Counting Reload
Value
DCEN = 1
Figure 16. 16-Bit Auto-reload Up/Down Counter
EXF2
T2CON.6
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Publication Release Date: September 1999
Revision A1