AT89LS52 datasheet(4/39 Pages) ATMEL

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AT89LS52

2601A–12/01

Pin Description

VCC

Supply voltage.

GND

Ground.

Port 0

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink eight

TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance

inputs.

Port 0 can also be configured to be the multiplexed low-order address/data bus during

accesses to external program and data memory. In this mode, P0 has internal pull-ups.

Port 0 also receives the code bytes during Flash programming and outputs the code bytes

during program verification. External pull-ups are required during program verification.

Port 1

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers can

sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being

pulled low will source current (I

IL) because of the internal pull-ups.

In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input

(P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the fol-

lowing table.

Port 1 also receives the low-order address bytes during Flash programming and verification.

Port 2

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output buffers can

sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being

pulled low will source current (I

IL) because of the internal pull-ups.

Port 2 emits the high-order address byte during fetches from external program memory and

during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this

application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to external

data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Spe-

cial Function Register.

Port 2 also receives the high-order address bits and some control signals during Flash pro-

gramming and verification.

Port 3

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the

internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being

pulled low will source current (I

IL) because of the pull-ups.

Port 3 receives some control signals for Flash programming and verification.

Port Pin

Alternate Functions

P1.0

T2 (external count input to Timer/Counter 2), clock-out

P1.1

T2EX (Timer/Counter 2 capture/reload trigger and direction control)

P1.5

MOSI (used for In-System Programming)

P1.6

MISO (used for In-System Programming)

P1.7

SCK (used for In-System Programming)

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