4
04-02-004I
PEELTM 16CV8
Design Security
The PEELTM 16CV8 provides a special EEPROM security bit that pre-
vents unauthorized reading or copying of designs programmed into the
device. The security bit is set by the PLD programmer, either at the con-
clusion of the programming cycle or as a separate step, after the device
has been programmed. Once the security bit has been set it is impossi-
ble to verify (read) or program the PEELTM until the entire device has
first been erased with the bulk-erase function.
Signature Word
The signature word feature allows a 64-bit code to be programmed into
the PEELTM 16CV8. The code cannot be read back after the security bit
has been set. The signature word can be used to identify the pattern
programmed into the device or to record the design revision, etc.
OE PIN
CLK PIN
DQ
Q
Registered Mode
Active High Registered Output
2
PRODUCT TERM
Registered Mode
Active Low Combinatorial Output
3
PRODUCT TERM
Registered Mode
Active High Combinatorial Output
4
OE PIN
CLK PIN
DQ
Q
Registered Mode
Active Low Registered Output
1
Complex Mode
In Complex mode, seven product terms feed the OR array which can
generate a purely combinatorial function for the output pin. The pro-
grammable output polarity selector provides active-high or active-low
logic, eliminating the need for external inverters. The output buffer is
controlled by the eighth product term, allowing the macrocell to be con-
figured for input, output, or bidirectional functions. Feedback into the
array for input or bidirectional functions is available on all pins except 12
and 19. Figure 4 shows the possible complex mode macrocell configura-
tions. Figure 7 shows the logic array of the PEELTM 16CV8 configured in
Complex mode.
Registered Mode
Registered mode provides eight product terms to the OR array for regis-
tered functions. The programmable output polarity selector provides
active-high or active-low logic, eliminating the need for external invert-
ers. (Note, however, that if register is selected, the PEELTM 16CV8 reg-
isters power-up reset and so before the first clock arrives the output at
the pin will be low if the user has selected active-high logic and high if
the user has selected active-low logic. If combinatorial is selected, the
output will be a function of the logic.) For registered functions, the output
buffer enable is controlled directly from the /OE control pin. Feedback
into the array comes from the macrocell register. In Registered mode,
input pins 1 and 11 are permanently allocated as CLK and /OE, respec-
tively. Figure 8 shows the logic array of the PEELTM 16CV8 configured in
Registered mode.
Registered mode also provides the option of configuring a macrocell for
combinatorial operation, with seven product terms feeding the OR func-
tion.
Again the programmable output polarity selector provides active-high or
active-low logic. The output buffer enable is controlled by the eighth
product term, allowing the macrocell to be configured for input, output, or
bidirectional functions. Feedback into the array for input or bidirectional
functions is available on all I/O pins. Macrocell Configurations for the
Registered Mode of the PEELTM 16CV8
PRODUCT TERM
Complex Mode
Active Low Output
1
PRODUCT TERM
Complex Mode
Active High Output
2
Figure 4 - Macrocell Configurations for the Complex Mode of the
PEELTM 16CV8 (see Figure 7 for Logic Array)
Figure 5 - Macrocell Configurations for the Registered Mode of
the PEELTM 16CV8 (see Figure 8 for logic Array)
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