Sonic Alert msm83c154s, msm80154s, msm85c154hvs Bit is 0, and valid when, Mode 1 or 3 has been set

MSM80C154S/83C154S/85C154HVS

4.5.3Timer/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)

Bit			7	6	5	4	3	2	1	0
Flag			TF2	EXF2	RCLK	TCLK	EXEN2	TR2	C/ T2	CP/ RL2
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/
C/T2		RL2 data is ignored when TCLK+RCLK=1.
	:	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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