Philips P89LPC908, P89LPC906, P89LPC907 user manual Tcon

Philips Semiconductors	User’s Manual - Preliminary -
TIMERS 0 AND 1	P89LPC906/907/908
MODE 3

When Timer 1 is in Mode 3 it is stopped. The effect is the same as setting TR1 = 0.

Timer 0 in Mode 3 establishes TL0 and TH0 as two separate 8-bit counters. The logic for Mode 3 on Timer 0 is shown in Figure 5-7. TL0 uses the Timer 0 control bits: TR0 and TF0. TH0 is locked into a timer function (counting machine cycles) and takes over the use of TR1 and TF1 from Timer 1. Thus, TH0 now controls the “Timer 1” interrupt.

Mode 3 is provided for applications that require an extra 8-bit timer.

Note: When Timer 0 is in Mode 3, Timer 1 can be turned on and off by switching it into and out of its own Mode 3. It can still be used by the serial port as a baud rate generator (P89LPC907,P89LPC908), or in any application not requiring an interrupt.

MODE 6 - P89LPC907

In this mode, Timer 0 can be changed to a PWM with a full period of 256 timer clocks (see Figure 5-8). Its structure is similar to mode 2, except that:

•TF0 is set and cleared in hardware;

•The low period of the TF0 is in TH0, and should be between 1 and 254, and;

•The high period of the TF0 is always 256-TH0.

•Loading TH0 with 00h will force the T0 pin high, loading TH0 with FFh will force the T0 pin low.

Note that an interrupt can still be enabled on the low to high transition of TF0, and that TF0 can still be cleared in software as in any other modes.

TCON		7		6	5	4	3	2	1	0
Address: 88h			TF1	TR1	TF0	TR0	-	-	-	-
Bit addressable
Reset Source(s): Any reset
Reset Value: 00000000B
BIT	SYMBOL	FUNCTION
TCON.7	TF1	Timer 1 overflow flag. Set by hardware on Timer overflow. Cleared by hardware when the
		interrupt is processed, or by software.
TCON.6	TR1	Timer 1 Run control bit. Set/cleared by software to turn Timer 1 on/off.
TCON.5	TF0	Timer 0 overflow flag. Set by hardware on Timer/Counter overflow. Cleared by hardware
		when the processor vectors to the interrupt routine, or by software. (except in mode 6, see
		above, when it is cleared in hardware)
TCON.4	TR0	Timer 0 Run control bit. Set/cleared by software to turn Timer/Counter 0 on/off.
TCON.3	-	Reserved for future use. Should not be set to 1 by user programs.
TCON.2	-	Reserved for future use. Should not be set to 1 by user programs.
TCON.1	-	Reserved for future use. Should not be set to 1 by user programs.
TCON.0	-	Reserved for future use. Should not be set to 1 by user programs.

Figure 5-3: Timer/Counter Control register (TCON)

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