P89LPC985 datasheet(61/85 Pages) NXP

61 / 85 page

P89LPC980_982_983_985_2

Preliminary data sheet

Rev. 02 — 8 February 2010

61 of 85

NXP Semiconductors

P89LPC980/982/983/985

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

8.4.4 Auto scan, continuous conversion mode

Any combination of the eight input channels can be selected for conversion. A conversion

of each selected input will be performed and the result placed in the result register pair

which corresponds to the selected input channel. The user may select whether an

interrupt, if enabled, will be generated after either the first four conversions have occurred

or all selected channels have been converted. If the user selects to generate an interrupt

after the four input channels have been converted, a second interrupt will be generated

after the remaining input channels have been converted. 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 eight result register pairs, overwriting the

previous results. Continuous conversions continue until terminated by the user.

8.4.5 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

the result register pair, AD0DAT0R and AD0DAT0L. The result of the conversion of the

second channel is placed in result register pair, AD0DAT1R and AD0DAT1L. The first

channel is again converted and its result stored in AD0DAT2R and AD0DAT2L. The

second channel is again converted and its result placed in AD0DAT3R and AD0DAT3L.

An interrupt is generated, if enabled, after every set of four or eight conversions (user

selectable).

8.4.6 Single step mode

This special mode allows ‘single-stepping’ in an auto scan conversion mode. Any

combination of the eight 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.

8.5 Conversion start modes

8.5.1 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 ADC operating modes.

8.5.2 Start immediately

Programming this mode immediately starts a conversion. This start mode is available in all

ADC operating modes.

8.5.3 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 ADC operating modes.

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