TS80C51RA2-VCKB datasheet(48/74 Pages) ATMEL

Part #	TS80C51RA2-VCKB

Description	High Performance 8-bit Microcontrollers

PDF	74 Pages

Scroll/Zoom	100%

Manufacturer	ATMEL [ATMEL Corporation]

Direct Link	http://www.atmel.com

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48 / 74 page

Rev. C - 06 March, 2001

TS80C51RA2/RD2

TS83C51RB2/RC2/RD2

TS87C51RB2/RC2/RD2

6.11. ONCETM Mode (ON Chip Emulation)

The ONCE mode facilitates testing and debugging of systems using TS80C51Rx2 without removing the circuit

from the board. The ONCE mode is invoked by driving certain pins of the TS80C51Rx2; the following sequence

must be exercised:

• Pull ALE low while the device is in reset (RST high) and PSEN is high.

• Hold ALE low as RST is deactivated.

While the TS80C51Rx2 is in ONCE mode, an emulator or test CPU can be used to drive the circuit Table 26.

shows the status of the port pins during ONCE mode.

Normal operation is restored when normal reset is applied.

Table 25. External Pin Status during ONCE Mode

ALE

PSEN

Port 0

Port 1

Port 2

Port 3

XTAL1/2

Weak pull-up

Float

Weak pull-up

Active

TS80C51RA2-VCKB Datasheet(PDF) 48 Page - ATMEL Corporation