AT83SND1CXXX-ROTIL datasheet(9/212 Pages) ATMEL

9 / 212 page

4109J–8051–10/06

AT8xC51SND1C

Table 11. Keypad Interface Signal Description

Table 12. External Access Signal Description

Notes:

1. For ROM/Flash Dice product versions: pad EA must be connected to VCC.

2. For ROMless Dice product versions: pad EA must be connected to VSS.

Table 13. System Signal Description

Signal

Name

Type

Description

Alternate

Function

KIN3:0

Keypad Input Lines

Holding one of these pins high or low for 24 oscillator periods triggers a

keypad interrupt.

P1.3:0

Signal

Name

Type

Description

Alternate

Function

A15:8

I/O

Address Lines

Upper address lines for the external bus.

Multiplexed higher address and data lines for the IDE interface.

P2.7:0

AD7:0

I/O

Address/Data Lines

Multiplexed lower address and data lines for the external memory or the

IDE interface.

P0.7:0

ALE

Address Latch Enable Output

ALE signals the start of an external bus cycle and indicates that valid

address information is available on lines A7:0. An external latch is used

to demultiplex the address from address/data bus.

PSEN

I/O

Program Store Enable Output (AT80C51SND1C Only)

This signal is active low during external code fetch or external code

read (MOVC instruction).

ISP

I/O

ISP Enable Input (AT89C51SND1C Only)

This signal must be held to GND through a pull-down resistor at the

falling reset to force execution of the internal bootloader.

Read Signal

Read signal asserted during external data memory read operation.

P3.7

Write Signal

Write signal asserted during external data memory write operation.

P3.6

(1)(2)

External Access Enable (Dice Only)

EA must be externally held low to enable the device to fetch code from

external program memory locations 0000h to FFFFh.

Signal

Name

Type

Description

Alternate

Function

RST

Reset Input

Holding this pin high 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 V

IL is applied, whether or not the

oscillator is running.

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

reset by connecting a capacitor between this pin and V

DD.

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

returns the chip to normal operation.

TST

Test Input

Test mode entry signal. This pin must be set to V

DD.

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