- Enhanced Architecture fits more logic than ordinary PLDs
General Description
The PEEL™18CV8 is a Programmable Electrically Erasable
Logic (PEEL™) device providing an attractive alternative to
ordinary PLDs. The PEEL™18CV8 offers the performance, flex-
ibility, ease of design and production practicality needed by logic
designers today.
The PEEL™18CV8 is available in 20-pin DIP, PLCC, SOIC and
TSSOP packages with speeds ranging from 7ns to 25ns with
power consumption as low as 37mA. EE-Reprogrammability
provides the convenience of instant reprogramming for develop-
ment and reusable production inventory minimizing the impact of
programming changes or errors. EE-Reprogrammability also
improves factory testability, thus assuring the highest quality pos-
sible.
The PEEL™18CV8 architecture allows it to replace over 20 stan-
dard 20-pin PLDs (PAL, GAL, EPLD etc.). It also provides addi-
tional architecture features so more logic can be put into every
design. Anachip’s JEDEC file translator instantly converts to the
PEEL™18CV8 existing 20-pin PLDs without the need to rework
the existing design. Development and programming support for the
PEEL™18CV8 is provided by popular third-party program- mers
and development software.
Figure 3 Block Diagram
Figure 2 Pin Configuration
I/CLK
I
I
I
I
I
I
I
I
GND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
VCC
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I
™
DIP
TSSOP
PLCC
SOIC
This datasheet contains new product information. Anachip Corp. reserves the rights to modify the product specification without notice. No liability is assumed as a result of the use of this product. No rights under any patent
accompany the sale of the product.
Rev. 1.0 Dec 16, 2004
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Not recommended for New designs -
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Figure 4 PEEL™18CV8 Logic Array Diagram
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Rev. 1.0 Dec 16, 2004
Not recommended for New designs -
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Function Description
The PEEL™18CV8 implements logic functions as sum-of- prod-
ucts expressions in a programmable-AND/fixed-OR logic array.
User-defined functions are created by programming the connec-
tions of input signals into the array. User-configurable output
structures in the form of I/O macrocells further increase logic
flexibility.
effect on the output function).
Programmable I/O Macrocell
The unique twelve-configuration output macrocell provides com-
plete control over the architecture of each output. The ability to
configure each output independently permits users to tailor the
configuration of the PEEL™18CV8 to the precise requirements of
their designs.
Architecture Overview
The PEEL™18CV8 architecture is illustrated in the block dia-
gram of Figure 3. Ten dedicated inputs and 8 I/Os provide up to
18 inputs and 8 outputs for creation of logic functions. At the core
of the device is a programmable electrically-erasable AND array
which drives a fixed OR array. With this structure, the
PEEL™18CV8 can implement up to 8 sum-of-products logic
expressions.
Associated with each of the 8 OR functions is an I/O macrocell
which can be independently programmed to one of 12 different
configurations. The programmable macrocells allow each I/O to
create sequential or combinatorial logic functions of active-high or
active-low polarity, while providing three different feedback paths
into the AND array.
Macrocell Architecture
Each I/O macrocell, as shown in Figure 4, consists of a D-type
flip-flop and two signal-select multiplexers. The configuration of
each macrocell is determined by the four EEPROM bits control-
ling these multiplexers. These bits determine output polarity, out-
put type (registered or non-registered) and input-feedback path
(bidirectional I/O, combinatorial feedback). Refer to Table 1 for
details.
Equivalent circuits for the twelve macrocell configurations are
illustrated in Figure 4. In addition to emulating the four PAL-type
output structures (configurations 3,4,9, and 10), the macrocell
provides eight additional configurations. When creating a
PEEL™ device design, the desired macrocell configuration gen-
erally is specified explicitly in the design file. When the design is
assembled or compiled, the macrocell configuration bits are
defined in the last lines of the JEDEC programming file.
AND/OR LOGIC ARRAY
The programmable AND array of the PEEL™18CV8 (shown in
Figure 4) is formed by input lines intersecting product terms. The
input lines and product terms are used as follows:
36 Input Lines:
- 20 input lines carry the true and complement of the signals
applied to the 10 input pins
- 16 additional lines carry the true and complement values of
feedback or input signals from the 8 I/Os
74 product terms:
- 64 product terms (arranged in groups of 8) are used to form
sum of product functions
- 8 output enable terms (one for each I/O)
- 1 global synchronous preset term
- 1 global asynchronous clear term
At each input-line/product-term intersection, there is an
EEPROM memory cell that determines whether or not there is a
logical connection at that intersection. Each product term is
essentially a 36-input AND gate. A product term that is con-
nected to both the true and complement of an input signal will
always be FALSE and thus will not affect the OR function that it
drives. When all the connections on a product term are opened, a
“don’t care” state exists and that term will always be TRUE. When
programming the PEEL™18CV8, the device programmer first
performs a bulk erase to remove the previous pattern. The erase
cycle opens every logical connection in the array. The device is
configured to perform the user-defined function by pro- gramming
selected connections in the AND array. (Note that PEEL™
device programmers automatically program all of the connections
on unused product terms so that they will have no
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Output Type
The signal from the OR array can be fed directly to the output pin
(combinatorial function) or latched in the D-type flip-flop (regis-
tered function). The D-type flip-flop latches data on the rising
edge of the clock and is controlled by the global preset and clear
terms. When the synchronous preset term is satisfied, the Q out-
put of the register will be set HIGH at the next rising edge of the
clock input. Satisfying the asynchronous clear will set Q LOW,
regardless of the clock state. If both terms are satisfied simulta-
neously, the clear will override the preset.
Output Polarity
Each macrocell can be configured to implement active-high or
active-low logic. Programmable polarity eliminates the need for
external inverters.
Output Enable
The output of each I/O macrocell can be enabled or disabled
under the control of its associated programmable output enable
product term. When the logical conditions programmed on the
output enable term are satisfied, the output signal is propagated to
the I/O pin. Otherwise, the output buffer is switched into the
high-impedance state.
Under the control of the output enable term, the I/O pin can func-
tion as a dedicated input, a dedicated output, or a bi-directional I/ O.
Opening every connection on the output enable term will per-
manently enable the output buffer and yield a dedicated output.
Conversely, if every connection is intact, the enable term will
Rev. 1.0 Dec 16, 2004
Not recommended for New designs -
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always be logically false and the I/O will function as a dedicated
input.
Registered Feedback
Feedback also can be taken from the register, regardless of
whether the output function is to be combinatorial or registered.
When implementing a combinatorial output function, registered
feedback allows for the internal latching of states without giving
up the use of the external output.
Input/Feedback Select
The PEEL™18CV8 macrocell also provides control over the
feedback path. The input/feedback signal associated with each I/ O
macrocell may be obtained from three different locations; from the
I/O input pin, from the Q output of the flip-flop (registered
feedback), or directly from the OR gate (combinatorial feed-
back).
Design Security
The PEEL™18CV8 provides a special EEPROM security bit that
prevents unauthorized reading or copying of designs pro-
grammed into the device. The security bit is set by the PLD pro-
grammer, either at the conclusion of the programming cycle or as a
separate step, after the device has been programmed. Once the
security bit is set it is impossible to verify (read) or program the
PEEL™ until the entire device has first been erased with the
bulk-erase function.
Bi-directional I/O
The input/feedback signal is taken from the I/O pin when using the
pin as a dedicated input or as a bi-directional I/O. (Note that it is
possible to create a registered output function with a bi-direc-
tional I/O.)
Combinatorial Feedback
The signal-select multiplexer gives the macrocell the ability to
feedback the output of the OR gate, bypassing the output buffer,
regardless of whether the output function is registered or combi-
natorial. This feature allows the creation of asynchronous latches,
even when the output must be disabled. (Refer to configurations
5,6,7 and 8 in Figure 4.)
Programming Support
Anachip’s JEDEC file translator allows easy conversion of exist-
ing 20 pin PLD designs to the PEEL™18CV8, without the need
for redesign. Anachip also offers (for free) its proprietary Win-
PLACE software, an easy-to-use entry level PC-based software
development system.
Programming support includes all the popular third party pro-
grammers: BP Microsystems, System General, Logical Devices,
and numerous others.
Figure 4 Block Diagram of the PEEL™18CV8
I/O Macrocell
Anachip Corp.
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Rev. 1.0 Dec 16, 2004
Not recommended for New designs -
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Figure 4 Equivalent Circuits for the Twelve Configurations of the PEEL™18CV8 I/O Macrocell
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