P89LPC913 datasheet(36/66 Pages) NXP

36 / 66 page

P89LPC912_913_914_5

Product data sheet

Rev. 05 — 28 September 2007

36 of 66

NXP Semiconductors

P89LPC912/913/914

8-bit microcontrollers with two-clock 80C51 core

8.12.7 Additional port features

After power-up, all pins are in Input-Only mode. After power-up all I/O pins except P1.5,

may be conﬁgured by software.

• Pin P1.5 is input only.

• P1.2/T0 is conﬁgurable for either input-only or open-drain (P89LPC912, P89LPC914).

Every output on the P89LPC912/913/914 has been designed to sink typical LED drive

current. However, there is a maximum total output current for all ports which must not be

exceeded. Please refer to Table 13 “Static characteristics” for detailed speciﬁcations.

All port pins that can function as an output have slew rate controlled outputs to limit noise

generated by quickly switching output signals. The slew rate is factory-set to

approximately 10 ns rise and fall times.

8.13 Power monitoring functions

The P89LPC912/913/914 incorporates power monitoring functions designed to prevent

incorrect operation during initial power-up and power loss or reduction during operation.

This is accomplished with two hardware functions: Power-on detect and brownout detect.

8.13.1 Brownout detection

The brownout detect function determines if the power supply voltage drops below a

certain level. The default operation is for a brownout detection to cause a processor reset,

however, it may alternatively be conﬁgured to generate an interrupt.

Brownout detection may be enabled or disabled in software.

If brownout detection is enabled, the brownout condition occurs when VDD falls below the

brownout trip voltage, Vbo (see Table 13 “Static characteristics”), and is negated when VDD

rises above Vbo. If the P89LPC912/913/914 device is to operate with a power supply that

can be below 2.7 V, BOE should be left in the unprogrammed state so that the device can

operate at 2.4 V, otherwise continuous brownout reset may prevent the device from

operating.

For correct activation of Brownout detect, the VDD rise and fall times must be observed.

Please see Table 13 “Static characteristics” for speciﬁcations.

8.13.2 Power-on detection

The Power-on detect has a function similar to the brownout detect, but is designed to work

as power comes up initially, before the power supply voltage reaches a level where

brownout detect can work. The POF ﬂag in the RSTSRC register is set to indicate an

initial power-up condition. The POF ﬂag will remain set until cleared by software.

8.14 Power reduction modes

The P89LPC912/913/914 supports three different power reduction modes. These modes

are Idle mode, Power-down mode, and Total Power-down mode.

P89LPC913 Datasheet(PDF) 36 Page - NXP Semiconductors

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