MSM80C154S/83C154S/85C154HVS
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4.5.3 Timer/counter 2
4.5.3.1 Outline
Timer/counter 2 is equipped with 16-bit binary counting and Read/Write functions. This timer/
counter is controlled entirely by timer 2 control register (T2CON 0C8H).
The operating modes are 16-bit auto reload mode, capture mode, and baud rate generator
mode. Modes are specified by T2CON RCLK, TCLK, and CP/RL2 bits combinations.
The internal or external clock applied to the timer/counter 2 is specified by the C/T2 bit. And
starting and stopping of timer/counter 2 counting is controlled by the TR2 bit. Note that timer/
counter 2 counting is stopped in CPU power down mode where XTAL1·2 are stopped.
4.5.3.2 Timer 2 control register (T2CON)
The timer 2 control register (T2CON 0C8H) consists of the timer/counter 2 control bits, timer
2 internal flag (TF2), and timer 2 external flag (EXF2). The T2CON contents are outlined in
Table 4-12.
Table 4-12 Timer 2 control register (T2CON 0C8H)
76543210
TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2 CP/RL2
Bit
Flag
CP/RL2 : Capture mode is set when TCLK+RCLK=0 and CP/RL2=1. The timer/counter
2 contents are passed to the capture register (RCAP2L/RCAP2H) when the
level o the signal applied to the T2EX pin (bit 1 of port 1) is changed from “1” to
“0” with EXEN2-1.
16-bit auto reload mode is set when TCLK+RCLK=0 and CP/RL2=0. The CP/
RL2 data is ignored when TCLK+RCLK=1.
C/T2 : Timer/counter 2 clock input designation bit.
The internal clock is specified when this bit is “0” and the external clock is
specified
when “1”.
TR2 : Timer/counter 2 counting start and stop control bit.
Timer/counter 2 operation is stopped when this bit is “0”, and enabled when “1”
EXEN2 : The T2EX pin control bit. The signal applied to the T2EX pin is invalid when this
bit is “0”, and valid when “1”.
TCLK : Serial port transmit clock control bit. When this bit is set to “1”, timer/counter 2
is set to 16-bit auto reload operation mode, and the timer/counter 2 carry signal
activates the serial port transmit circuit. This clock is only valid when serial port
mode 1 or 3 has been set.
RCLK : Serial port receive clock control bit. When this bit is set to “1”, timer/counter 2
is set to 16-bit auto reload operation mode, and the timer/counter 2 carry signal
activates the serial port receive circuit.
This clock is only valid when serial port mode 1 or 3 has been set.
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