AT89C5131A-L View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT89C5131A-L

8-bit Flash Microcontroller with Full Speed USB Device

Atmel Corporation 

AT89C5131A-L

Table 10. USB Signal Description

Signal

Name Type Description

D+

D-

VREF

USB Data + signal

I/O

Set to high level under reset.

USB Data - signal

I/O

Set to low level under reset.

O

USB Reference Voltage

Connect this pin to D+ using a 1.5 kΩ resistor to use the Detach function.

Alternate

Function

-

-

-

Table 11. System Signal Description

Signal

Name Type Description

Alternate

Function

AD[7:0]

Multiplexed Address/Data LSB for external access

I/O

Data LSB for Slave port access (used for 8-bit and 16-bit modes)

P0[7:0]

A[15:8]

Address Bus MSB for external access

I/O

Data MSB for Slave port access (used for 16-bit mode only)

P2[7:0]

Read Signal

RD

I/O Read signal asserted during external data memory read operation.

Control input for slave port read access cycles.

P3.7

Write Signal

WR

I/O Write signal asserted during external data memory write operation.

Control input for slave write access cycles.

P3.6

Reset

Holding this pin low for 64 oscillator periods while the oscillator is running

resets the device. The Port pins are driven to their reset conditions when a

voltage lower than VIL is applied, whether or not the oscillator is running.

RST

I/O

This pin has an internal pull-up resistor which allows the device to be reset

by connecting a capacitor between this pin and VSS.

-

Asserting RST when the chip is in Idle mode or Power-down mode returns

the chip to normal operation.

This pin is set to 0 for at least 12 oscillator periods when an internal reset

occurs (hardware watchdog or Power monitor).

Address Latch Enable Output

ALE

O

The falling edge of ALE strobes the address into external latch. This signal

is active only when reading or writing external memory using MOVX

-

instructions.

Program Strobe Enable / Hardware conditions Input for ISP

PSEN

O Used as input under reset to detect external hardware conditions of ISP

-

mode

External Access Enable

EA

I This pin must be held low to force the device to fetch code from external

-

program memory starting at address 0000h. It is latched during reset and

cannot be dynamically changed during operation.

9

4338E–USB–06/06

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