ST6285 datasheet(16/76 Pages) STMICROELECTRONICS

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ST62T85B/E85B

1.4 PROGRAMMING MODES

1.4.1 Option Byte

The Option Byte allows configuration capability to

the MCUs. Option byte’s content is automatically

read, and the selected options enabled, when the

chip reset is activated.

It can only be accessed during the programming

mode. This access is made either automatically

(copy from a master device) or by selecting the

OPTION BYTE PROGRAMMING mode of the pro-

grammer.

The option byte is located in a non-user map. No

address has to be specified.

EPROM Code Option Byte

Bit 7-6. Reserved.

Bit 5= PROTECT. This bit allows the protection of

the software contents against piracy. When the bit

PROTECT is set high, readout of the OTP con-

tents is prevented by hardware. No programming

equipment is able to gain access to the user pro-

gram. When this bit is low, the user program can

be read.

Bit 4. Reserved.

Bit 3 = NMI PULL. . This bit must be set high to en-

able the internal pull-up resistor. When low, no

pull-up is provided.

Bit 2. Reserved.

Bit 1 = WDACT. This bit controls the watchdog ac-

tivation. When it is high, hardware activation is se-

lected. The software activation is selected when

WDACT is low.

Bit 0 = Reserved.

The Option byte is written during programming ei-

ther by using the PC menu (PC driven Mode) or

automatically (stand-alone mode)

1.4.2 Program Memory

EPROM/OTP programming mode is set by a

+12.5V voltage applied to the TEST/VPP pin. The

programming flow of the ST62T85B/E85B is de-

scribed in the User Manual of the EPROM Pro-

gramming Board.

The

MCUs

can

programmed

with

the

ST62E8xB EPROM programming tools available

from STMicroelectronics.

1.4.3 EEPROM Data Memory

EEPROM data pages are supplied in the virgin

state FFh. Partial or total programming of EEP-

ROM data memory can be performed either

through the application software, or through an ex-

ternal programmer. Any STMicroelectronics tool

used for the program memory (OTP/EPROM) can

also be used to program the EEPROM data mem-

ory.

1.4.4 EPROM Erasing

The EPROM of the windowed package of the

MCUs may be erased by exposure to Ultra Violet

light. The erasure characteristic of the MCUs is

such that erasure begins when the memory is ex-

posed to light with a wave lengths shorter than ap-

proximately 4000Å. It should be noted that sun-

lights and some types of fluorescent lamps have

wavelengths in the range 3000-4000Å.

It is thus recommended that the window of the

MCUs packages be covered by an opaque label to

prevent unintentional erasure problems when test-

ing the application in such an environment.

The recommended erasure procedure of the

MCUs EPROM is the exposure to short wave ul-

traviolet light which have a wave-length 2537A.

The integrated dose (i.e. U.V. intensity x exposure

time) for erasure should be a minimum of 15W-

sec/cm2. The erasure time with this dosage is ap-

proximately 15 to 20 minutes using an ultraviolet

lamp with 12000

µW/cm2 power rating. The

ST62E85B should be placed within 2.5cm (1Inch)

of the lamp tubes during erasure.

PRO-

TECT

NMI

PULL

WDACT

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