ST62T35B ST Microelectronics, ST62T35B Datasheet - Page 15

• Manufacturer Part Number: ST62T35B
• Description: (ST62E35B / ST62T35B) 8-BIT OTP/EPROM MCUs
• Manufacturer: ST Microelectronics

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
programmer.
The option byte is located in a non-user map. No
address has to be specified.
EPROM Code Option Byte
Bit 7. Reserved.
Bit 6 = PORT PULL . This bit must be set high to
have pull-up input state at reset on the I/O port.
When this bit is low, I/O ports are in input without
pull-up (high impedance) state at reset
Bit 5 = EXTCNTL . This bit selects the External
STOP Mode capability. When EXTCNTL is high,
pin NMI controls if the STOP mode can be ac-
cessed when the watchdog is active. When
EXTCNTL is low, the STOP instruction is proc-
essed as a WAIT as soon as the watchdog is ac-
tive.
Bit 4 = 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 3 = TIM PULL. This bit must be set high to con-
figure the TIMER pin with a pull up resistor. When
it is low, no pull up is provided.
Bit 2 = NMI PULL. This bit must be set high to con-
figure the NMI pin with a pull up resistor when it is
low, no pull up is provided.
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.
7
-
PORT
PULL
EXTC NTL PROTECT
PULL
TIM
PULL
NMI
WDACT OSGEN
0
Bit 0 = OSGEN. This bit must be set high to enable
the oscillator Safe Guard. When this bit is low, the
OSG is disabled.
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/V
programming flow of the ST62T35B is described
in the User Manual of the EPROM Programming
Board.
The MCUs can be programmed
ST62E3xB EPROM programming tools available
from SGS-THOMSON.
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 SGS-THOMSON 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/cm
proximately 15 to 20 minutes using an ultraviolet
lamp with 12000 W/cm
ST62E35B should be placed within 2.5cm (1Inch)
of the lamp tubes during erasure.
2
. The erasure time with this dosage is ap-
2
power rating. The
ST62T35B/E35B
PP
with the
pin. The
15/82
14