Rainbow-electronics AT89LP216 Bedienungsanleitung PDF herunterladen (Seite 22)

3621A–MICRO–6/06

AT89LP216 [Preliminary]

13. I/O Ports

The AT89LP216 can be configured for between 9 and 12 I/O pins. The exact number of I/O pins

available depends on the clock and reset options as shown in Table 13-1. All port pins are 5V

tolerant, that is they can be pulled up or driven to 5.5V even when operating at a lower V

such

as 3V.

13.1 Port Configuration

All port pins on the AT89LP216 may be configured to one of four modes: quasi-bidirectional

(standard 8051 port outputs), push-pull output, open-drain output, or input-only. Port modes may

be assigned in software on a pin-by-pin basis as shown in Table 13-2. The Tristate-Port User

Fuse determines the default state of the port pins. When the fuse is enabled, all port pins default

to input-only mode after reset. When the fuse is disabled, all port pins, with the exception of P1.0

and P1.1, default to quasi-bidirectional mode after reset and are weakly pulled high. Each port

pin also has a Schmitt-triggered input for improved input noise rejection. During Power-down all

the Schmitt-triggered inputs are disabled with the exception of P1.3, P3.2 and P3.3, which may

be used to wake up the device. Therefore, P1.3, P3.2 and P3.3 should not be left floating during

Power-down

Table 13-1. I/O Pin Configurations

Clock Source Reset Option Number of I/O Pins

External Crystal or Resonator

External RST

Pin 11

No external reset 12

External Clock

External RST

Pin 12

No external reset 13

Internal RC Oscillator

External RST

Pin 13

No external reset 14

Table 13-2. Configuration Modes for Port x, Bit y

PxM0.y PxM1.y Port Mode

0 0 Quasi-bidirectional

0 1 Push-pull Output

1 0 Input Only (High Impedance)

1 1 Open-Drain Output

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 89 90

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