AT89C51ED2-RDTIM datasheet(11/137 Pages) ATMEL

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AT89C51RD2/ED2

4235E–8051–04/04

Table 13. Pin Description

Mnemonic

Pin Number

Type

Name and Function

PLCC44 VQFP44

PLCC68

VQFP64

PDIL40

Ground: 0V reference

VCC

Power Supply: This is the power supply voltage for normal, idle and

power-down operation

P0.0 - P0.7

43 - 36

37 - 30

15, 14,

12, 11,

9,6, 5, 3

6, 5, 3,

2, 64,

61,60,59

I/O

Port 0: Port 0 is an open-drain, bidirectional I/O port. Port 0 pins that

have 1s written to them float and can be used as high impedance inputs.

Port 0 must be polarized to V

CC or VSS in order to prevent any parasitic

current consumption. Port 0 is also the multiplexed low-order address

and data bus during access to external program and data memory. In this

application, it uses strong internal pull-up when emitting 1s. Port 0 also

inputs the code bytes during EPROM programming. External pull-ups are

required during program verification during which P0 outputs the code

bytes.

32-39

P1.0 - P1.7

2 - 9

40 - 44

1 - 3

19, 21,

22, 23,

25, 27,

28, 29

10, 12,

13, 14,

16, 18,

19, 20

1-8

I/O

Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. Port 1

pins that have 1s written to them are pulled high by the internal pull-ups

and can be used as inputs. As inputs, Port 1 pins that are externally

pulled low will source current because of the internal pull-ups. Port 1 also

receives the low-order address byte during memory programming and

verification.

Alternate functions for AT89C51RD2/ED2 Port 1 include:

240

I/O

P1.0: Input/Output

I/O

T2 (P1.0): Timer/Counter 2 external count input/Clockout

341

I/O

P1.1: Input/Output

T2EX: Timer/Counter 2 Reload/Capture/Direction Control

SS: SPI Slave Select

442

I/O

P1.2: Input/Output

ECI: External Clock for the PCA

543

I/O

P1.3: Input/Output

I/O

CEX0: Capture/Compare External I/O for PCA module 0

644

I/O

P1.4: Input/Output

I/O

CEX1: Capture/Compare External I/O for PCA module 1

I/O

P1.5: Input/Output

I/O

CEX2: Capture/Compare External I/O for PCA module 2

I/O

MISO: SPI Master Input Slave Output line

When SPI is in master mode, MISO receives data from the slave periph-

eral. When SPI is in slave mode, MISO outputs data to the master con-

troller.

I/O

P1.6: Input/Output

I/O

CEX3: Capture/Compare External I/O for PCA module 3

I/O

SCK: SPI Serial Clock

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