TSC80251G2D
8. Programming and Verifying Non-Volatile Memory
8.1 Internal Features
The internal non-volatile memory of the TSC80251G2D derivatives contains five different areas:
● Code Memory
● Configuration Bytes
● Lock Bits
● Encryption Array
● Signature Bytes
8.1.1 EPROM/OTPROM Devices
All the internal non-volatile memory but the Signature Bytes of the TSC87251G2D products is made of EPROM
cells. The Signature Bytes of the TSC87251G2D products are made of Mask ROM.
The TSC87251G2D products are programmed and verified in the same manner as TEMIC’s TSC87251G1A, using
a SINGLE-PULSE algorithm, which programs at V = 12.75V using only one 100 µs pulse per byte. This results
PP
in a programming time of less than 10 seconds for the 32 Kbytes on-chip code memory.
(1)
The EPROM of the TSC87251G2D products in Window package is erasable by Ultra-Violet radiation (UV).
UV erasure set all the EPROM memory cells to one and allows a reprogramming. The quartz window must be
(2)
covered with an opaque label when the device is in operation. This is not so much to protect the EPROM array
from inadvertent erasure, as to protect the RAM and other on-chip logic. Allowing light to impinge on the silicon
die during device operation may cause a logical malfunction.
The TSC87251G2D products in plastic packages are One Time Programmable (OTP). Then an EPROM cell cannot
be reset by UV once programmed to zero.
Notes:
2
1. The recommended erasure procedure is exposure to ultra-violet light (at 2537 Å) to an integrated dose of at least 20 W-sec/cm . Exposing
2
the EPROM to an ultra-violet lamp of 12000 µW/cm rating for 30 minutes should be sufficient.
2. Erasure of the EPROM begins to occur when the chip is exposed to light wavelength shorter than 4000 Å. Since sunlight and fluorescent
light have wavelength in this range, exposure to these light sources over an extended time (1 week in sunlight or 3 years in room-level
fluorescent lighting) could cause inadvertent erasure.
8.1.2 Mask ROM Devices
All the internal non-volatile memory of TSC83251G2D products is made of Mask ROM cells. They can only be
verified by the user, using the same algorithm as the EPROM/OTPROM devices.
8.1.3 ROMless Devices
The TSC80251G2D products do not include on-chip Configuration Bytes, Code Memory and Encryption Array.
They only include Signature Bytes made of Mask ROM cells which can be read using the same algorithm as the
EPROM/OTPROM devices.
8.2 Security Features
In some microcontrollers applications, it is desirable that the user’s program code be secured from unauthorized
access. The TSC83251G2D and TSC87251G2D offer two kinds of protection for program code stored in the on-
chip array:
● Program code in the on-chip Code Memory is encrypted when read out for verification if the Encryption Array is
programmed.
● A three-level lock bit system restricts external access to the on-chip code memory.
Rev. A - May 7, 1999
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TEMIC [ TEMIC SEMICONDUCTORS ]
