83C751 datasheet(18/24 Pages) PHILIPS

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Philips Semiconductors

Product specification

83C751/87C751

80C51 8-bit microcontroller family

2K/64 OTP/ROM, I2C, low pin count

1998 May 01

Programming and Verifying Security Bits

Security bits are programmed employing the same techniques used

to program the USER EPROM and KEY arrays using serial data

streams and logic levels on port pins indicated in Table 6. When

programming either security bit, it is not necessary to provide

address or data information to the 87C751 on ports 1 and 3.

Verification occurs in a similar manner using the RESET serial

stream shown in Table 6. Port 3 is not required to be driven and the

results of the verify operation will appear on ports 1.6 and 1.7.

Ports 1.7 contains the security bit 1 data and is a logical one if

programmed and a logical zero if not programmed. Likewise, P1.6

contains the security bit 2 data and is a logical one if programmed

and a logical zero if not programmed.

Erasure Characteristics

Erasure of the EPROM begins to occur when the chip is exposed to

light with wavelengths shorter than approximately 4,000 angstroms.

Since sunlight and fluorescent lighting have wavelengths in this

range, exposure to these light sources over an extended time (about

1 week in sunlight, or 3 years in room level fluorescent lighting)

could cause inadvertent erasure. For this and secondary effects,

it is recommended that an opaque label be placed over the

window. For elevated temperature or environments where solvents

are being used, apply Kapton tape Flourless part number 2345–5 or

equivalent.

The recommended erasure procedure is exposure to ultraviolet light

(at 2537 angstroms) to an integrated dose of at least 15W-s/cm2.

Exposing the EPROM to an ultraviolet lamp of 12,000

µW/cm2 rating

for 20 to 39 minutes, at a distance of about 1 inch, should be

sufficient.

Erasure leaves the array in an all 1s state.

Table 6. Implementing Program/Verify Modes

OPERATION

SERIAL CODE

P0.1 (PGM/)

P0.2 (VPP)

Program user EPROM

296H

–*

VPP

Verify user EPROM

296H

VIH

Program key EPROM

292H

–*

VPP

Verify key EPROM

292H

VIH

Program security bit 1

29AH

–*

VPP

Program security bit 2

298H

–*

VPP

Verify security bits

29AH

VIH

NOTE:

Pulsed from VIH to VIL and returned to VIH.

A0–A10

ADDRESS STROBE

PROGRAMMING

PULSES

VPP/VIH VOLTAGE

SOURCE

CLK SOURCE

RESET

CONTROL

LOGIC

87C751

P3.0–P3.7

P0.0/ASEL

P0.1

P0.2

XTAL1

RESET

VCC

VSS

P1.0–P1.7

+5V

DATA BUS

SU00317

Figure 5. Programming Configuration

MIN 2 MACHINE

CYCLES

TEN BIT SERIAL CODE

BIT 0

BIT 1

BIT 2

BIT 3

BIT 4

BIT 5

BIT 6

BIT 7

BIT 8

BIT 9

UNDEFINED

XTAL1

RESET

P0.2

P0.1

SU00302

Figure 6. Entry into Program/Verify Modes

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