P89LPC9211FDH datasheet(50/75 Pages) NXP

50 / 75 page

P89LPC92X1

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Product data sheet

Rev. 2 — 1 December 2010

50 of 75

NXP Semiconductors

P89LPC9201/9211/922A1/9241/

8-bit microcontroller with 8-bit ADC

8.7 Boundary limits interrupt

Each of the A/D converters has both a high and low boundary limit register. The user may

select whether an interrupt is generated when the conversion result is within (or equal to)

the high and low boundary limits or when the conversion result is outside the boundary

limits. An interrupt will be generated, if enabled, if the result meets the selected interrupt

criteria. The boundary limit may be disabled by clearing the boundary limit interrupt

enable.

An early detection mechanism exists when the interrupt criteria has been selected to be

outside the boundary limits. In this case, after the four MSBs have been converted, these

four bits are compared with the four MSBs of the boundary high and low registers. If the

four MSBs of the conversion meet the interrupt criteria (i.e., outside the boundary limits)

an interrupt will be generated, if enabled. If the four MSBs do not meet the interrupt

criteria, the boundary limits will again be compared after all 8 bits have been converted.

The boundary status register (BNDSTA0) flags the channels which caused a boundary

interrupt.

8.8 DAC output to a port pin with high output impedance

The DAC block of ADC1 can be output to a port pin. In this mode, the AD1DAT3 register is

used to hold the value fed to the DAC. After a value has been written to the DAC (written

to AD1DAT3), the DAC output will appear on the channel 3 pin.

8.9 Clock divider

The ADC requires that its internal clock source be in the range of 320 kHz to 8 MHz to

maintain accuracy. A programmable clock divider that divides the clock from 1 to 8 is

provided for this purpose.

8.10 Power-down and Idle mode

In Idle mode the ADC, if enabled, will continue to function and can cause the device to exit

Idle mode when the conversion is completed if the A/D interrupt is enabled. In

Power-down mode or Total Power-down mode, the A/D and temperature sensor do not

function. If temperature sensor or the A/D are enabled, they will consume power. Power

can be reduced by disabling temperature sensor and A/D.

P89LPC9211FDH Datasheet(PDF) 50 Page - NXP Semiconductors