4 of 10

04-02-010F

enable term will permanently enable the output buffer and

yield a dedicated output. Conversely, if every connection is

intact, the enable term will always be logically false and the

I/O will function as a dedicated input.

Input/Feedback Select

When configuring an I/O macrocell to implement a regis-

tered function (configurations 1 and 2 in Figure 5), the Q

output of the flip-flop drives the feedback term. When con-

figuring an I/O macrocell to implement a combinatorial

function (configurations 3 and 4 in Figure 5), the feedback

signal is taken from the I/O pin. In this case, the pin can be

used as a dedicated input or a bi-directional I/O. (Refer

also to Table 1.)

Additional Macro Cell Configurations

Besides the standard four-configuration macrocell shown in

Figure 5, each PEEL™22CV10A provides an additional

eight configurations that can be used to increase design

flexibility. The configurations are the same as provided by

the PEEL™18CV8 and PEEL™22CV10AZ. However, to

maintain JEDEC file compatibility with standard 22V10

PLDs the additional configurations can only be utilized by

specifying the PEEL™22CV10A+ and PEEL22CV10A++

for logic assembly and programming. To reference these

additional configurations please refer to the specifications

at the end of this data sheet.

Design Security

The PEEL™22CV10A provides a special EEPROM secu-

rity bit that prevents unauthorized reading or copying of

designs programmed into the device. The security bit is set

by the PLD programmer, either at the conclusion of the pro-

gramming cycle or as a separate step after the device has

been programmed. Once the security bit is set, it is impos-

sible to verify (read) or program the PEEL™ until the entire

device has first been erased with the bulk-erase function.

Signature Word

The signature word feature allows a 24-bit code to be pro-

grammed

into

the

PEEL™22CV10A

if

the

PEEL™22CV10A+ software option is used. Also, the sig-

nature word feature allows a 64-bit code to be programmed

into the PEEL™22CV10A if the PEEL™22CV10A++ soft-

ware option is used. The code can be read back even 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.

Figure 4. Block Diagram of the PEEL™ 22CV10A I/O Macrocell.