16R8
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16RP4
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16RP6
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14RP8
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Programmable Macrocell
The macrocell provides complete control over the
architecture of each output. The ability to configure
each output independently permits users to tailor
the configuration of the PEEL16V8 to the precise
requirements of their designs.
Macrocell Architecture
Each macrocell consists of an OR function, a D-type
flip-flop, an output polarity selector, and a program-
mable feedback path. Four EEPROM architecture
bits MS0, MS1, OP and RC control the configuration
of each macrocell. Bits MS0 and MS1 are global,
and select between Simple, Complex and Regis-
tered mode for the whole device. Bits OP and RC
are local for each macrocell; bit OP controls the
output polarity and bit RC selects between regis-
tered and combinatorial operation and also speci-
fies the feedback path. Table 2 shows the architec-
ture bit settings for each possible configuration.
Equivalent circuits for the possible macrocell con-
figurations are illustrated in Figures 3, 4 and 5.
When creating a PEEL device design, the desired
macrocell configuration generally is specified explic-
itly 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.
Simple Mode
In Simple mode, all eight product terms feed the OR
array which can generate a purely combinatorial
function for the output pin. The programmable out-
put polarity selector allows active-high or active-low
logic, eliminating the need for external inverters.
For output functions, the buffer can be permanently
enabled. Feedback into the array is available on all
macrocell I/O pins, except for pins 15 and 16. Figure
VCC
Simple Mode
Active Low Output
1
VCC
Simple Mode
Active High Output
2
Simple Mode
I/O Pin Input
3
Figure 3. Macrocell Configurations for the Simple
Mode of the PEEL16V8
Table 2. PEEL16V8 Device Mode/Macrocell Architecture Configuration Bits
Config.
Mode
Architecture Bits
Function
Polarity
Feedback
#MS0
MS1
OP
RC
1
Simple
1000
Combinatorial
Active Low
I/O Pin
2
Simple
1010
Combinatorial
Active High
I/O Pin
3
Simple
1
0
X
1
None
None
I/O Pin
1
Complex
1101
Combinatorial
Active Low
I/O Pin
2
Complex
1111
Combinatorial
Active High
I/O Pin
1
Registered
0100
Registered
Active Low
Registered
2
Registered
0110
Registered
Active High
Registered
3
Registered
0101
Combinatorial
Active Low
I/O Pin
4
Registered
0111
Combinatorial
Active High
I/O Pin
PEEL™ 16V8
3-9