
4
Specifications GAL20V8
The following discussion pertains to configuring the output logic
macrocell. It should be noted that actual implementation is accom-
plished by development software/hardware and is completely trans-
parent to the user.
There are three global OLMC configuration modes possible:
simple, complex, and registered. Details of each of these modes
is illustrated in the following pages. Two global bits, SYN and AC0,
control the mode configuration for all macrocells. The XOR bit of
each macrocell controls the polarity of the output in any of the three
modes, while the AC1 bit of each of the macrocells controls the in-
put/output configuration. These two global and 16 individual archi-
tecture bits define all possible configurations in a GAL20V8 . The
information given on these architecture bits is only to give a bet-
ter understanding of the device. Compiler software will transpar-
ently set these architecture bits from the pin definitions, so the user
should not need to directly manipulate these architecture bits.
The following is a list of the PAL architectures that the GAL20V8
can emulate. It also shows the OLMC mode under which the
devices emulate the PAL architecture.
Software compilers support the three different global OLMC modes
as different device types. These device types are listed in the table
below. Most compilers have the ability to automatically select the
device type, generally based on the register usage and output
enable (OE) usage. Register usage on the device forces the soft-
ware to choose the registered mode. All combinatorial outputs with
OE controlled by the product term will force the software to choose
the complex mode. The software will choose the simple mode only
when all outputs are dedicated combinatorial without OE control.
The different device types listed in the table can be used to override
the automatic device selection by the software. For further details,
refer to the compiler software manuals.
When using compiler software to configure the device, the user
must pay special attention to the following restrictions in each mode.
In registered mode pin 1 and pin 13 (DIP pinout) are permanently
configured as clock and output enable, respectively. These pins
cannot be configured as dedicated inputs in the registered mode.
In complex mode pin 1 and pin 13 become dedicated inputs and
use the feedback paths of pin 22 and pin 15 respectively. Because
of this feedback path usage, pin 22 and pin 15 do not have the
feedback option in this mode.
In simple mode all feedback paths of the output pins are routed
via the adjacent pins. In doing so, the two inner most pins ( pins
18 and 19) will not have the feedback option as these pins are
always configured as dedicated combinatorial output.
Registered Complex Simple Auto Mode Select
ABEL P20V8R P20V8C P20V8AS P20V8
CUPL G20V8MS G20V8MA G20V8AS G20V8
LOG/iC GAL20V8_R GAL20V8_C7 GAL20V8_C8 GAL20V8
OrCAD-PLD "Registered"1"Complex"1"Simple"1GAL20V8A
PLDesigner P20V8R2P20V8C2P20V8C2P20V8A
TANGO-PLD G20V8R G20V8C G20V8AS3G20V8
1) Used with Configuration keyword.
2) Prior to Version 2.0 support.
3) Supported on Version 1.20 or later.
P AL Architectures GAL20V8
Emulated by GAL20V8 Global OLMC Mode
20R8 Registered
20R6 Registered
20R4 Registered
20RP8 Registered
20RP6 Registered
20RP4 Registered
20L8 Complex
20H8 Complex
20P8 Complex
14L8 Simple
16L6 Simple
18L4 Simple
20L2 Simple
14H8 Simple
16H6 Simple
18H4 Simple
20H2 Simple
14P8 Simple
16P6 Simple
18P4 Simple
20P2 Simple
Output Logic Macrocell (OLMC)
Compiler Support for OLMC