SC83C451CGA68 datasheet(18/22 Pages) PHILIPS

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Philips Semiconductors

Product specification

80C451/83C451/87C451

80C51 8-bit microcontroller family

4K/128 OTP/ROM/ROMless, expanded I/O

1998 May 01

EPROM CHARACTERISTICS

The 87C451 is programmed by using a modified Quick-Pulse

Programming

™ algorithm. It differs from older methods in the value

used for VPP (programming supply voltage) and in the width and

number of the ALE/PROG pulses.

The 87C451 contains two signature bytes that can be read and used

by an EPROM programming system to identify the device. The

signature bytes identify the device as an 87C451 manufactured by

Philips Semiconductors.

Table 4 shows the logic levels for reading the signature byte, and for

programming the program memory, the encryption table, and the

lock bits. The circuit configuration and waveforms for quick-pulse

programming are shown in Figures 18 and 19. Figure 20 shows the

circuit configuration for normal program memory verification.

Quick-Pulse Programming

The setup for microcontroller quick-pulse programming is shown in

Figure 18. Note that the 87C451 is running with a 4 to 6MHz

oscillator. The reason the oscillator needs to be running is that the

device is executing internal address and program data transfers.

The address of the EPROM location to be programmed is applied to

ports 1 and 2, as shown in Figure 18. The code byte to be

programmed into that location is applied to port 0. RST, PSEN and

pins of ports 2 and 3 specified in Table 4 are held at the ‘Program

Code Data’ levels indicated in Table 4. The ALE/PROG is pulsed

low 25 times as shown in Figure 19.

To program the encryption table, repeat the 25 pulse programming

sequence for addresses 0 through 1FH, using the ‘Pgm Encryption

Table’ levels. Do not forget that after the encryption table is

programmed, verification cycles will produce only encrypted data.

To program the lock bits, repeat the 25 pulse programming

sequence using the ‘Pgm Lock Bit’ levels. After one lock bit is

programmed, further programming of the code memory and

encryption table is disabled. However, the other lock bit can still be

programmed.

Note that the EA/VPP pin must not be allowed to go above the

maximum specified VPP level for any amount of time. Even a narrow

glitch above that voltage can cause permanent damage to the

device. The VPP source should be well regulated and free of glitches

and overshoot.

Program Verification

If lock bit 2 has not been programmed, the on-chip program memory

can be read out for program verification. The address of the program

memory locations to be read is applied to ports 1 and 2 as shown in

Figure 20. The other pins are held at the ‘Verify Code Data’ levels

indicated in Table 4. The contents of the address location will be

emitted on port 0. External pull-ups are required on port 0 for this

operation.

If the encryption table has been programmed, the data presented at

port 0 will be the exclusive NOR of the program byte with one of the

encryption bytes. The user will have to know the encryption table

contents in order to correctly decode the verification data. The

encryption table itself cannot be read out.

Reading the Signature Bytes

The signature bytes are read by the same procedure as a normal

verification of locations 030H and 031H, except that P3.6 and P3.7

need to be pulled to a logic low. The values are:

(030H) = 15H indicates manufactured by Philips

(031H) = 90H indicates 87C451

Program/Verify Algorithms

Any algorithm in agreement with the conditions listed in Table 4, and

which satisfies the timing specifications, is suitable.

Table 4. EPROM Programming Modes

MODE

RST

PSEN

ALE/PROG

EA/VPP

P2.7

P2.6

P3.7

P3.6

Read signature

Program code data

VPP

Verify code data

Pgm encryption table

VPP

Pgm lock bit 1

VPP

Pgm lock bit 2

VPP

NOTES:

1. ‘0’ = Valid low for that pin, ‘1’ = valid high for that pin.

2. VPP = 12.75V ±0.25V.

3. VCC = 5V ±10% during programming and verification.

ALE/PROG receives 25 programming pulses while VPP is held at 12.75V. Each programming pulse is low for 100µs (±10µs) and high for a

minimum of 10

µs.

™Trademark phrase of Intel Corporation.

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