Description
The ATF1508ASV(L) is a high-performance, high-density
complex programmable logic device (CPLD) that utilizes
Atmel’s proven electrically-erasable technology. With 128
logic macrocells and up to 100 inputs, it easily integrates
logic from several TTL, SSI, MSI, LSI and classic PLDs.
The ATF1508ASV(L)’s enhanced routing switch matrices
increase usable gate count and increase odds of success-
ful pin-locked design modifications.
Product Terms and Select Mux
Each ATF1508ASV(L) macrocell has five product terms.
Each product term receives as its inputs all signals from
both the global bus and regional bus.
The product term select multiplexer (PTMUX) allocates the
five product terms as needed to the macrocell logic gates
and control signals. The PTMUX programming is deter-
mined by the design compiler, which selects the optimum
macrocell configuration.
The ATF1508ASV(L) has up to 96 bi-directional I/O pins
and four dedicated input pins, depending on the type of
device package selected. Each dedicated pin can also
serve as a global control signal, register clock, register
reset or output enable. Each of these control signals can be
selected for use individually within each macrocell.
OR/XOR/CASCADE Logic
The ATF1508ASV(L)’s logic structure is designed to effi-
ciently support all types of logic. Within a single macrocell,
all the product terms can be routed to the OR gate, creating
a 5-input AND/OR sum term. With the addition of the
CASIN from neighboring macrocells, this can be expanded
to as many as 40 product terms with little additional delay.
Each of the 128 macrocells generates a buried feedback
that goes to the global bus. Each input and I/O pin also
feeds into the global bus. The switch matrix in each logic
block then selects 40 individual signals from the global bus.
Each macrocell also generates a foldback logic term that
goes to a regional bus. Cascade logic between macrocells
in the ATF1508ASV(L) allows fast, efficient generation of
complex logic functions. The ATF1508ASV(L) contains
eight such logic chains, each capable of creating sum term
logic with a fan-in of up to 40 product terms.
The macrocell’s XOR gate allows efficient implementation
of compare and arithmetic functions. One input to the XOR
comes from the OR sum term. The other XOR input can be
a product term or a fixed high- or low-level. For combinato-
rial outputs, the fixed level input allows polarity selection.
For registered functions, the fixed levels allow DeMorgan
minimization of product terms. The XOR gate is also used
to emulate T- and JK-type flip-flops.
The ATF1508ASV(L) macrocell, shown in Figure 1, is flexi-
ble enough to support highly-complex logic functions oper-
ating at high-speed. The macrocell consists of five
sections: product terms and product term select multi-
plexer, OR/XOR/CASCADE logic, a flip-flop, output select
and enable, and logic array inputs.
Flip-flop
The ATF1508ASV(L)’s flip-flop has very flexible data and
control functions. The data input can come from either the
XOR gate, from a separate product term or directly from
the I/O pin. Selecting the separate product term allows cre-
ation of a buried registered feedback within a combinatorial
output macrocell. (This feature is automatically imple-
mented by the fitter software). In addition to D, T, JK and
SR operation, the flip-flop can also be configured as a flow-
through latch. In this mode, data passes through when the
clock is high and is latched when the clock is low.
Unused macrocells are automatically disabled by the com-
piler to decrease power consumption. A security fuse,
when programmed, protects the contents of the
ATF1508ASV(L). Two bytes (16 bits) of User Signature are
accessible to the user for purposes such as storing project
name, part number, revision or date. The User Signature is
accessible regardless of the state of the security fuse.
The clock itself can either be the Global CLK Signal (GCK)
or an individual product term. The flip-flop changes state on
the clock's rising edge. When the GCK signal is used as
the clock, one of the macrocell product terms can be
selected as a clock enable. When the clock enable function
is active and the enable signal (product term) is low, all
clock edges are ignored. The flip-flop’s asynchronous reset
signal (AR) can be either the Global Clear (GCLEAR), a
product term, or always off. AR can also be a logic OR of
GCLEAR with a product term. The asynchronous preset
(AP) can be a product term or always off.
The ATF1508ASV(L) device is an in-system programmable
(ISP) device. It uses the industry-standard 4-pin JTAG
interface (IEEE Std. 1149.1), and is fully-compliant with
JTAG’s Boundary-scan Description Language (BSDL). ISP
allows the device to be programmed without removing it
from the printed circuit board. In addition to simplifying the
manufacturing flow, ISP also allows design modifications to
be made in the field via software.
ATF1508ASV(L)
4
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