PXAG30KBBD datasheet(13/36 Pages) PHILIPS

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Philips Semiconductors

Product data

XA-G30

XA 16-bit microcontroller family

512 B RAM, watchdog, 2 UARTs

2002 Mar 25

timer register is loaded with FFFF hex. The underflow also sets the

TF2 flag, which can generate an interrupt if enabled.

The external flag EXF2 toggles when Timer 2 underflows or

overflows. This EXF2 bit can be used as a 17th bit of resolution, if

needed. the EXF2 flag does not generate an interrupt in this mode.

As the baud rate generator, timer T2 is incremented by TCLK.

Baud Rate Generator Mode

By setting the TCLKn and/or RCLKn in T2CON or T2MOD, the

Timer 2 can be chosen as the baud rate generator for either or both

UARTs. The baud rates for transmit and receive can be

simultaneously different.

Programmable Clock-Out

A 50% duty cycle clock can be programmed to come out on P1.6.

This pin, besides being a regular I/O pin, has two alternate

functions. It can be programmed (1) to input the external clock for

Timer/Counter 2 or (2) to output a 50% duty cycle clock ranging from

3.58Hz to 3.75MHz at a 30MHz operating frequency.

To configure the Timer/Counter 2 as a clock generator, bit C/T2 (in

T2CON) must be cleared and bit T20E in T2MOD must be set. Bit

TR2 (T2CON.2) also must be set to start the timer.

The Clock-Out frequency depends on the oscillator frequency and

the reload value of Timer 2 capture registers (TCAP2H, TCAP2L) as

shown in this equation:

TCLK

(65536

* TCAP2H, TCAP2L)

In the Clock-Out mode Timer 2 roll-overs will not generate an

interrupt. This is similar to when it is used as a baud-rate generator.

It is possible to use Timer 2 as a baud-rate generator and a clock

generator simultaneously. Note, however, that the baud-rate will be

1/8 of the Clock-Out frequency.

Table 1. Timer 2 Operating Modes

TR2

CP/RL2

RCLK+TCLK

DCEN

MODE

Timer off (stopped)

16-bit auto-reload, counting up

16-bit auto-reload, counting up or down depending on T2EX pin

16-bit capture

Baud rate generator

T0OE

LSB

MSB

BIT

SYMBOL

FUNCTION

TSTAT.2

T1OE

When 0, this bit allows the T1 pin to clock Timer 1 when in the counter mode.

When 1, T1 acts as an output and toggles at every Timer 1 overflow.

TSTAT.0

T0OE

When 0, this bit allows the T0 pin to clock Timer 0 when in the counter mode.

When 1, T0 acts as an output and toggles at every Timer 0 overflow.

SU00612B

—

T1OE

—

TSTAT

Address:411

Bit Addressable

Reset Value: 00H

Figure 5. Timer 0 And 1 Extended Status (TSTAT)

DCEN

BIT

SYMBOL

FUNCTION

T2MOD.5 RCLK1

Receive Clock Flag.

T2MOD.4 TCLK1

Transmit Clock Flag. RCLK1 and TCLK1 are used to select Timer 2 overflow rate as a clock source

for UART1 instead of Timer T1.

T2MOD.1 T2OE

When 0, this bit allows the T2 pin to clock Timer 2 when in the counter mode.

When 1, T2 acts as an output and toggles at every Timer 2 overflow.

T2MOD.0 DCEN

Controls count direction for Timer 2 in autoreload mode.

DCEN=0 counter set to count up only

DCEN=1 counter set to count up or down, depending on T2EX (see text).

SU00610B

T2OE

—

TCLK1

RCLK1

—

T2MOD

Address:419

Bit Addressable

Reset Value: 00H

LSB

MSB

Figure 6. Timer 2 Mode Control (T2MOD)

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