P87LPC768FD datasheet(39/64 Pages) PHILIPS

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Philips Semiconductors

Preliminary data

87LPC768

Low power, low price, low pin count (20 pin) microcontroller

with 4 kB OTP 8-bit A/D, Pulse Width Modulator

2001 Aug 06

Mode 0

Putting either Timer into Mode 0 makes it look like an 8048 Timer,

which is an 8-bit Counter with a divide-by-32 prescaler. Figure 27

shows Mode 0 operation.

In this mode, the Timer register is configured as a 13-bit register. As

the count rolls over from all 1s to all 0s, it sets the Timer interrupt

flag TFn. The count input is enabled to the Timer when TRn = 1 and

either GATE = 0 or INTn = 1. (Setting GATE = 1 allows the Timer to

be controlled by external input INTn, to facilitate pulse width

measurements). TRn is a control bit in the Special Function Register

TCON (Figure 26). The GATE bit is in the TMOD register.

The 13-bit register consists of all 8 bits of THn and the lower 5 bits

of TLn. The upper 3 bits of TLn are indeterminate and should be

ignored. Setting the run flag (TRn) does not clear the registers.

Mode 0 operation is the same for Timer 0 and Timer 1. See

Figure 27. There are two different GATE bits, one for Timer 1

(TMOD.7) and one for Timer 0 (TMOD.3).

BIT

SYMBOL

FUNCTION

TCON.7

TF1

Timer 1 overflow flag. Set by hardware on Timer/Counter 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/Counter 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.

TCON.4

TR0

Timer 0 Run control bit. Set/cleared by software to turn Timer/Counter 0 on/off.

TCON.3

IE1

Interrupt 1 Edge flag. Set by hardware when external interrupt 1 edge is detected. Cleared by

hardware when the interrupt is processed, or by software.

TCON.2

IT1

Interrupt 1 Type control bit. Set/cleared by software to specify falling edge/low level triggered

external interrupts.

TCON.1

IE0

Interrupt 0 Edge flag. Set by hardware when external interrupt 0 edge is detected. Cleared by

hardware when the interrupt is processed, or by software.

TCON.0

IT0

Interrupt 0 Type control bit. Set/cleared by software to specify falling edge/low level triggered

external interrupts.

IT0

SU01172

IE0

IT1

IE1

TR0

TF0

TR1

TF1

TCON

Reset Value: 00h

Bit Addressable

Address: 88h

Figure 26. Timer/Counter Control Register (TCON)

SU01173

TLN

(5-BITS)

THN

(8-BITS)

OSC/6

OSC/12

OVERFLOW

Tn PIN

TnOE

TOGGLE

CONTROL

C/T = 1

C/T = 0

Tn PIN

TRn

GATE

INTn PIN

INTERRUPT

TFn

Figure 27. Timer/Counter 0 or 1 in Mode 0 (13-Bit Counter)

P87LPC768FD Datasheet(PDF) 39 Page - NXP Semiconductors

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