GAL20RA10 LATTICE [Lattice Semiconductor], GAL20RA10 Datasheet - Page 10

• Manufacturer Part Number: GAL20RA10
• Manufacturer: LATTICE [Lattice Semiconductor]

An electronic signature word is provided in every GAL20RA10
device. It contains 64 bits of reprogrammable memory that con-
tains user defined data. Some uses include user ID codes, revi-
sion numbers, pattern identification or inventory control codes. The
signature data is always available to the user independent of the
state of the security cell.
NOTE: The electronic signature bits if programmed to any value
other then zero(0) will alter the checksum of the device.
A security cell is provided in every GAL20RA10 device as a deter-
rent to unauthorized copying of the device pattern. Once pro-
grammed, this cell prevents further read access of the device
pattern information. This cell can be only be reset by reprogram-
ming the device. The original pattern can never be examined once
this cell is programmed. The Electronic Signature is always avail-
able regardless of the security cell state.
GAL20RA10 devices are designed with an on-board charge pump
to negatively bias the substrate. The negative bias is of sufficient
magnitude to prevent input undershoots from causing the circuitry
to latch. Additionally, outputs are designed with n-channel pullups
instead of the traditional p-channel pullups to eliminate any pos-
sibility of SCR induced latching.
Electronic Signature
Security Cell
Latch-Up Protection
10
GAL devices are programmed using a Lattice Semiconductor-
approved Logic Programmer, available from a number of manu-
facturers (see the the GAL Development Tools section). Complete
programming of the device takes only a few seconds. Erasing of
the device is transparent to the user, and is done automatically as
part of the programming cycle.
GAL20RA10 devices are designed with TTL level compatible in-
put buffers. These buffers have a characteristically high impedance
and present a much lighter load to the driving logic than traditional
bipolar devices.
GAL20RA10 input buffers have active pull-ups within their input
structure. As a result, unused inputs and I/Os will float to a TTL
“high” (logical “1”). Lattice Semiconductor recommends that all un-
used inputs and tri-stated I/O pins be connected to another active
input, Vcc, or GND. Doing this will tend to improve noise immu-
nity and reduce Icc for the device.
Device Programming
Input Buffers
Specifications GAL20RA10
- 2 0
- 4 0
- 6 0
0
0
Typical Input Pull-up Characteristic
1 . 0
In p u t V o lt ag e ( V o lt s)
2 . 0
3 . 0
4 . 0
5 . 0