P87LPC778FDH datasheet(36/79 Pages) PHILIPS

36 / 79 page

Philips Semiconductors

P87LPC778

CMOS single-chip 8-bit microcontroller

Product data

Rev. 01 — 31 March 2004

36 of 79

9397 750 12378

8.9.3

Push-pull output conﬁguration

The push-pull output conﬁguration has the same pulldown structure as both the open

drain and the quasi-bidirectional output modes, but provides a continuous strong

pull-up when the port latch contains a logic 1. The push-pull mode may be used when

more source current is needed from a port output.

The push-pull port conﬁguration is shown in Figure 12.

The three port pins that cannot be conﬁgured are P1.2, P1.3, and P1.5. The port pins

P1.2 and P1.3 are permanently conﬁgured as open drain outputs. They may be used

as inputs by writing ones to their respective port latches. P1.5 may be used as a

Schmitt trigger input if the P87LPC778 has been conﬁgured for an internal reset and

is not using the external reset input function RST.

Additionally, port pins P2.0 and P2.1 are disabled for both input and output if one of

the crystal oscillator options is chosen. Those options are described in Section 8.10

“Oscillator” on page 39.

Fig 11. Open drain output.

002aaa629

port latch

data

input

data

port

Fig 12. Push-pull output.

002aaa630

port latch

data

input

data

port

VDD

P87LPC778FDH Datasheet(PDF) 36 Page - NXP Semiconductors