P89LPC904FD datasheet(18/41 Pages) PHILIPS

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Philips Semiconductors

P89LPC904

8-bit microcontrollers with two-clock accelerated 80C51 core

Preliminary data

Rev. 02 — 25 June 2004

18 of 41

9397 750 13521

selected input channel. An interrupt, if enabled, will be generated after all selected

channels have been converted. The process will repeat starting with the ﬁrst selected

channel. Additional conversion results will again cycle through the four result

registers, overwriting the previous results.Continous conversions continue until

terminated by the user.

Dual channel, continuous conversion mode: This is a variation of the auto scan

continuous conversion mode where conversion occurs on two user-selectable inputs.

The result of the conversion of the ﬁrst channel is placed in result register, AD1DAT0.

The result of the conversion of the second channel is placed in result register,

AD1DAT1. The ﬁrst channel is again converted and its result stored in AD1DAT2. The

second channel is again converted and its result placed in AD1DAT3. An interrupt is

generated, if enabled, after every set of four conversions (two conversions per

channel).

Single step mode: This special mode allows ‘single-stepping’ in an auto scan

conversion mode. Any combination of the four input channels can be selected for

conversion. After each channel is converted, an interrupt is generated, if enabled,

and the A/D waits for the next start condition. May be used with any of the start

modes.

8.9.4

Conversion start modes

Timer triggered start: An A/D conversion is started by the overﬂow of Timer 0. Once

a conversion has started, additional Timer 0 triggers are ignored until the conversion

has completed. The Timer triggered start mode is available in all A/D operating

modes.

Start immediately: Programming this mode immediately starts a conversion.This

start mode is available in all A/D operating modes.

Edge triggered: An A/D conversion is started by rising or falling edge of P1.4. Once

a conversion has started, additional edge triggers are ignored until the conversion

has completed. The edge triggered start mode is available in all A/D operating

modes.

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