W79E648 Datasheet, PDF (44/80 Pages) Winbond – Fast 8051 Compatible microcontroller with a redesigned Processor

Preliminary W79E648
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.
T2M = CKCON.5
osc
1/4
C/T = T2CON.1
1
0
1/12 ₀
1
T2 = P1.0
TR2 = T2CON.2
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
Baud Rate Generator Mode
The baud rate generator mode is enabled by setting either the RCLK or TCLK bits in T2CON register.
While in the baud rate generator mode, Timer/Counter 2 is a 16 bit counter with auto reload when the
count rolls over from FFFFh. However, rolling over does not set the TF2 bit. If EXEN2 bit is set, then a
negative transition of the T2EX pin will set EXF2 bit in the T2CON register and cause an interrupt
request.
osc
T2 = P1.0
TR2 = T2CON.2
C/T = T2CON.1
0
1
TL2 TH2
Timer 2
overflow
T2EX = P1.1
EXEN2 = T2CON.3
RCAP2L RCAP2H
Figure 17. Baud Rate Generator Mode
EXF2
T2CON.6
Timer 2
Interrupt
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