Intel 80C196NU, 8XC196NP T1CONTROL, Clock Source Direction Source, Prescaler Divisor Resolution †

8XC196NP, 80C196NU USER’S MANUAL

T1CONTROL	Address:	1F90H
	Reset State:	00H

The timer 1 control (T1CONTROL) register determines the clock source, counting direction, and count rate for timer 1.

7

CE UD M2 M1

0

M0 P2 P1 P0

Bit	Bit					Function
Number	Mnemonic
7	CE	Counter Enable
		This bit enables or disables the timer. From reset, the timers are
		disabled and not free running.
		0	= disables timer
		1	= enables timer
6	UD	Up/Down
		This bit determines the timer counting direction, in selected modes (see
		mode bits, M2:0).
		0	= count down
		1	= count up
5:3	M2:0	EPA Clock Direction Mode Bits
		These bits determine the timer clocking source and direction control
		source.
		M2		M1	M0	Clock Source	Direction Source
		0		0	0	f/4	UD bit (T1CONTROL.6)
		X		0	1	T1CLK pin†	UD bit (T1CONTROL.6)
		0		1	0	f/4	T1DIR pin
		0		1	1	T1CLK pin†	T1DIR pin
		1		1	1	quadrature clocking using T1CLK and T1DIR
		†	If an external clock is selected, the timer counts on both the rising and
		falling edges of the clock.
2:0	P2:0	EPA Clock Prescaler Bits
		These bits determine the clock prescaler value.
		P2		P1	P0	Prescaler Divisor		Resolution†
		0		0	0	divide by 1 (disabled)		160 ns
		0		0	1	divide by 2		320 ns
		0		1	0	divide by 4		640 ns
		0		1	1	divide by 8		1.28 µs
		1		0	0	divide by 16		2.56 µs
		1		0	1	divide by 32		5.12 µs
		1		1	0	divide by 64		10.24 µs
		1		1	1	divide by 128 (NU only)		20.48 µs

†At f = 25 MHz. Use the formula on page 10-6 to calculate the resolution at other frequencies.

Figure 10-8. Timer 1 Control (T1CONTROL) Register

10-16