programming selected connections in the AND array. (Note
that PEEL™ device programmers automatically program
the connections on unused product terms so that they will
have no effect on the output function.)
Function Description
The PEEL™22CV10A implements logic functions as sum-
of-products expressions in a programmable-AND/ fixed-OR
logic array. User-defined functions are created by program-
ming the connections of input signals into the array. User-
configurable output structures in the form of I/O macrocells
further increase logic flexibility.
Variable Product Term Distribution
The PEEL™22CV10A provides 120 product terms to drive
the 10 OR functions. These product terms are distributed
among the outputs in groups of 8, 10, 12, 14 and 16 to form
logical sums (see Figure 3). This distribution allows opti-
mum use of device re-sources.
Architecture Overview
The PEEL™22CV10A architecture is illustrated in the block
diagram of Figure 2. Twelve dedicated inputs and 10 I/Os
provide up to 22 inputs and 10 outputs for creation of logic
functions. At the core of the device is a programmable elec-
trically-erasable AND array which drives a fixed OR array.
With this structure, the PEEL™22CV10A can implement up
to 10 sum-of-products logic expressions.
Programmable I/O Macrocell
The output macrocell provides complete control over the
architecture of each output. The ability to configure each
output independently permits users to tailor the configura-
tion of the PEEL™22CV10A to the precise requirements of
their designs.
Associated with each of the 10 OR functions is an I/O mac-
rocell which can be independently programmed to one of 4
different configurations. The programmable macrocells
allow each I/O to create sequential or combinatorial logic
functions with either active-high or active-low polarity.
Macrocell Architecture
Each I/O macrocell, as shown in Figure 4, consists of a D-
type flip-flop and two signal-select multiplexers. The config-
uration of each macrocell is determined by the two
EEPROM bits controlling these multiplexers (refer to Table
1). These bits determine output polarity and output type
(registered or non-registered). Equivalent circuits for the
four macro-cell configurations are illustrated in Figure 5.
AND/OR Logic Array
The programmable AND array of the PEEL™22CV10A
(shown in Figure 3) is formed by input lines intersecting
product terms. The input lines and product terms are used as
follows:
Output Type
44 Input Lines:
The signal from the OR array can be fed directly to the out-
put pin (combinatorial function) or latched in the D-type flip-
flop (registered function). The D-type flip-flop latches data on
the rising edge of the clock and is controlled by the glo- bal
preset and clear terms. When the synchronous preset term
is satisfied, the Q output of the register will be set HIGH at
the next rising edge of the clock input. Satisfying the
asynchronous clear term will set Q LOW, regardless of the
clock state. If both terms are satisfied simultaneously, the
clear will override the preset.
24 input lines carry the true and complement
of the signals applied to the 12 input pins
20 additional lines carry the true and complement
values of feedback or input signals from
the 10 I/Os
132 product terms:
120 product terms (arranged in 2 groups of 8,
10, 12, 14 and 16) used to form logical sums
10 output enable terms (one for each I/O)
1 global synchronous present term
Output Polarity
Each macrocell can be configured to implement active-high
or active-low logic. Programmable polarity eliminates the
need for external inverters.
1 global asynchronous clear term
At each input-line/product-term intersection there is an
EEPROM memory cell which determines whether or not
there is a logical connection at that intersection. Each prod-
uct term is essentially a 44-input AND gate. A product term
which is connected 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™22CV10A, 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
then configured to perform the user-defined function by
Output Enable
The output of each I/O macrocell can be enabled or dis-
abled 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 driven into the high-impedance state.
Under the control of the output enable term, the I/O pin can
function as a dedicated input, a dedicated output, or a bi-
directional I/O. Opening every connection on the output
Anachip Corp.
www.anachip.com.tw
Rev. 1.0 Dec 16, 2004
3/10
ANACHIP [ ANACHIP CORP ]
