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P80C557E6

Single-chip 8-bit microcontroller

Philips Electronics 

Philips Semiconductors

Single-chip 8-bit microcontroller

Product specification

P83C557E6/P80C557E6

6.4 I/O Facilities

The P8xC557E6 has six 8–bit ports. Ports 0 to 3 are the same as in

the 80C51, with the exception of the additional functions of Port 1.

The parallel I/O function of Port 4 is equal to that of Ports 1, 2 and 3.

Port 5 has a parallel input port function, but has no function as an

output port.

The SDA and SCL lines serve the serial port SI01 (I2C). Because

the I2C–bus may be active while the device is disconnected from

VDD, these pins, are provided with open drain drivers.

Ports 0, 1, 2, 3, 4 and 5 perform the following alternative functions:

Port 0 :

Port 1 :

Port 2 :

Port 3 :

provides the multiplexed low–order address and

data bus used for expanding the P8xC557E6 with

standard memories and peripherals.

Port 1 is used for a number of special functions:

4 capture inputs (or external interrupt request inputs

if capture information is not utilized)

– external counter input

– external counter reset input

provides the high–order address bus when the

P8xC557E6 is expanded with external Program

Memory and/or external Data Memory.

pins can be configured individually to provide:

– external interrupt request inputs

– counter inputs

– receiver input and transmitter output of seri port

SIO 0 (UART)

– control signals to read and write external Data

Memory

Port 4 :

Port 5 :

can be configured to provide signals indicating a

match between timer counter T2 and its compare

registers.

may be used in conjunction with the ADC inter-

face.Unused analog inputs can be used as digital

inputs. As Port 5 lines may be used as inputs to the

ADC, these digital inputs have an inherent hystere-

sis to prevent the input logic from drawing too much

current from the power lines when driven by analog

signals. Channel to channel crosstalk should be tak-

en into consideration when both digital and analog

signals are simultaneously input to Port 5 (see DC

characteristics).

All ports are bidirectional with the exception of Port 5 which is an

input port.

Pins of which the alternative function is not used may be used as

normal bidirectional I/Os.

The generation or use of a Port 1, Port 3 or Port 4 pin as an

alternative function is carried out automatically by the P8xC557E6

provided the associated Special Function Register bit is set HIGH.

The pull–up arrangements of Ports 1 – 4 are shown in Figure 9.

2 System Clock Periods

VDD

VDD

VDD

P1

P2

P3

QN

From Port

Latch

Port

Pin

n

Input Data

Read Port Pin

P1 is turned on for 2 system clock periods after QN makes a 1–to–0 transition.

During this time, P1 also turns on P3 through the inverter to form an additional pull up.

Figure 9. I/O buffers in the P8xC557E6 (Ports 1, 2, 3 and 4).

1999 Mar 02

15

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