Realtek RTD2120-series
confidential
12
RCAP2H
CBh
TL2
CCh
TH2
CDh
1.
16-bit timer/counter with capture
The Timer 2 capture mode is the same as the 16-bit timer/counter with the addition of the capture
registers and control signals. If EXEN2 = 0, Timer2 is a 16-bit timer/counter . The C/T2 bit determines
whether the 16-bit counter counts osc cycles (divided by 4 or 12), or high-to-low transitions on the
P1.0 pin. The TR2 bit enables the counter. When the count increments from FFFFh, the TF2 flag is set.
The CP/RL2 bit in the T2CON SFR enables the capture feature. When CP/RL2 = 1, a high-to-low
transition on P1.1 when EXEN2 = 1 causes the Timer 2 value to be loaded into the capture registers
(RCAP2L and RCAP2H).
2.
16-bit timer/counter with auto-reload
When CP/RL2 = 0, Timer 2 is configured for the auto-reload mode. Control of counter input is the
same as for the other 16-bit counter modes. When the count increments from FFFFh, Timer 2 sets the
TF2 flag and the starting value is reloaded into TL2 and TH2. The software must preload the starting
value into the RCAP2L and RCAP2H registers. When Timer 2 is in auto-reload mode, a reload can be
forced by a high-to-low transition on the P1.1 pin, if enabled by EXEN2 = 1.
3.
Baud rate generator
Setting either RCLK or TCLK to 1 configures Timer 2 to generate baud rates for Serial Port 0 in
serial mode 1 or 3. In baud rate generator mode, Timer 2 functions in auto-reload mode. However,
instead of setting the TF2 flag, the counter overflow generates a shift clock for the serial port function.
As in normal auto-reload mode, the overflow also causes the preloaded start value in the RCAP2L and
RCAP2H registers to be reloaded into the TL2 and TH2 registers. When either TCLK = 1 or RCLK =
1, Timer 2 is forced into auto-reload operation, regardless of the state of the CP/RL2 bit. When
operating as a baud rate generator, Timer 2 does not set the TF2 bit. In this mode, a Timer 2 interrupt
can only be generated by a high-to-low transition on the P1.1 pin setting the EXF2 bit, and only if
enabled by EXEN2 = 1.
The counter time base in baud rate generator mode is osc/2. To use an external clock source,
set C/T2 to 1 and apply the desired clock source to the P1.0 pin.
Special Function Registers(SFR)
Register
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
Value
(Hex)
Addr
(Hex)
SP
07
81
DPL0
00
82
DPH0
00
83
DPL1
00
84
DPH1
00
85
DPS
0
0
0
0
0
0
0
SEL
00
86
PCON
SMOD0
1
1
GF1
GF0
STOP
IDLE
30
87
TCON
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
00
88
TMOD
GATE
C/T
M1
M0
GATE
C/T
M1
M0
00
89
TL0
00
8A
