Specifications
GAL20V8
Output Logic Macrocell (OLMC)
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.
PAL Architectures
Emulated by GAL20V8
20R8
20R6
20R4
20RP8
20RP6
20RP4
20L8
20H8
20P8
14L8
16L6
18L4
20L2
14H8
16H6
18H4
20H2
14P8
16P6
18P4
20P2
GAL20V8
Global OLMC Mode
Registered
Registered
Registered
Registered
Registered
Registered
Complex
Complex
Complex
Simple
Simple
Simple
Simple
Simple
Simple
Simple
Simple
Simple
Simple
Simple
Simple
Select devices have been discontinued.
See Ordering Information section for product status.
Compiler Support for OLMC
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
ABEL
CUPL
LOG/iC
OrCAD-PLD
PLDesigner
TANGO-PLD
P20V8R
G20V8MS
GAL20V8_R
"Registered"
1
P20V8R
2
G20V8R
Complex
P20V8C
G20V8MA
GAL20V8_C7
"Complex"
1
P20V8C
2
G20V8C
Simple
P20V8AS
G20V8AS
GAL20V8_C8
"Simple"
1
P20V8C
2
G20V8AS
3
Auto Mode Select
P20V8
G20V8
GAL20V8
GAL20V8A
P20V8A
G20V8
1) Used with
Configuration
keyword.
2) Prior to Version 2.0 support.
3) Supported on Version 1.20 or later.
4
LATTICE [ LATTICE SEMICONDUCTOR ]
