ATV2500B
11
Security Fuse Usage
A single fuse is provided to pre vent unauthorized copying
of ATV2500B fuse patterns. Once programmed, the outputs will read programmed during verify. The security
fuse should be programmed last, as its effect is immediate.
The security fuse also inhibits Preload and Q2 observability.
Atmel CMOS PLDs
The ATV2500Bs utilize an advanced 0.65-micron CMOS
EPROM technology. This technology's state of the art features are the optimum combination for PLDs:
• CMO S technology provides high speed, low power, and
high noise immunity.
• EP ROM technolo gy is the most cost effective method for
producing PLDs - surpassing bipolar fusible link
technology in low cost, while providing the necessary
reprogrammability.
• EP ROM reprogrammability, which is 100% tested before
shipment, provides inherently better programmability and
reliability than one-time fusible PLDs.
Using the ATV2500Bs Many Advanced
Features
The ATV2500B s advanc ed flexib ility pac ks more u sable
gates into 44 leads th an other PLDs. Some of the
ATV2500Bs key features are:
• Fully Connected Logic Array -
Each array input is alw ays availa ble to eve ry product term.
This makes logic placement a breeze.
• Selectable D- and T-Type Registers -
Each ATV2500B flip-flop can be individually configured as
either D- or T-type. Using the T-type configuration, JK and
SR flip-flops are also easily created. These options allow
more efficient product term usage.
• Buried Combinatorial Feedback -
Each macrocell's Q2 register may be bypassed to feed its
input (D/T2) directly back to the logic array. This provides
further logic expansion capability without using precious pin
resources.
• Selectable Synchronous/Asynchronous Clocking -
Each of the ATV2500B s flip-flops has a dedicated c lock
product term. This r emoves th e const raint that al l regis ters
use the same clock. B uried state machi nes, counters and
registers can all coexist in one device while running on separate clocks. Individual flip-flop clock source selection further allows mixing higher performance pin clocking and
flexible product term clocking within one design.
• A Total of 48 Registers The ATV2500B provides two flip-flops per macrocell - a
total of 48. Each register has its own clock and reset terms,
as well as its own sum term.
• Independent I/O Pin and Feedback Paths Each I/O pin on th e ATV 2500 B has a de di ca ted in put path.
Each of the 48 registers has its own feedback term into the
array as well. These features, combined with individual
product terms for each I/O's output enable, facilitate true bidirectional I/O design.
• Combinable Sum Terms Each output macrocell's three sum terms may be combined
into a single term. This provides a fan in of up to 12 product
terms per sum term with
no speed penalty
.
Programming Software Support
As with all other Atmel PLDs, several third party PLD development software products and programmers will support
the ATV2500Bs.
Several third party programmers will support the
ATV2500B as well. Additionally, the ATV2500B may be
programmed to perform the ATV2500H/Ls functional subset (no T-type flip-flops, pin clocking or D/T2 feedback)
using the ATV2500H/L JEDEC file. In this case, the
ATV2500B becomes a direct r eplacement or speed
upgrade for the ATV2500H/L (additional GND connections
are required). Please refer to the Programmable Logic
Development Tools section for a complete PLD software
and programmer listing.
Erasure Characteristics
The entire memory array of an ATV 2500B is eras ed after
exposure to ultraviolet light at a wavel ength of 2537 Å.
Complete erasure is assured after a minimum of 20 minutes exposure using 12,000
µW/cm
2
intensity lamps
spaced one inch away from the chip. Minimum erase time
for lamps at other intensity ratings can be calc ulated from
the minimum inte grated erasur e dose of 1 5 W
•
sec/cm2. To
prevent unintentional erasure, an opaque label is recommended to cover the clear window on any UV erasable
PLD which will be subjected to continuous fluorescent
indoor lighting or sunligh t.