Functional Block Diagram. I 8 OLMC. Pin Configuration. High speed erase times. The generic architecture provides maximum design flexibility by.

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Note: The development software configures all of the architecture control bits and checks for proper pin usage automatically.

See Input Buffer section for more information. Characterized initially and after any design or process changes that may affect these. A security cell is provided in the GAL20V8 devices to prevent unauthorized. There are three global OLMC configuration modes possible: simple, complex, and registered. Details of each of these modes is illustrated in the following pages. These two global and 16 individual architecture bits define all possible configurations in a GAL20V8.

The information given on these architecture bits is only to give a better understanding of the device. Compiler software will transparently set these architecture bits from the pin definitions, so the user should not need to directly manipulate these architecture bits. 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 software 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. 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.

When using compiler software to configure the device, the user must pay special attention to the following restrictions in each mode. All registered macrocells share common clock and output enable control pins. Registered outputs have eight product terms per output. Architecture configurations available in this mode are similar to the common 20L8 and 20P8 devices with programmable polarity in each macrocell.

All macrocells have seven product terms per output. One product term is used for programmable output enable control. Pins 1 and 13 are always available as data inputs into the AND array. Architecture configurations available in this mode are similar to the common 14L8 and 16P6 devices with many permutations of generic output polarity or input choices. All outputs in the simple mode have a maximum of eight product terms that can control the logic. In addition, each output has programmable polarity.

These are stress only ratings and functional operation of the device at these or at any other conditions above those indicated in the operational sections of this specification is not implied while programming, follow the programming specifications. Refer to fmax Descriptions section. Characterized initially and after any design or process changes that may affect these parameters.

The value of tcf is used primarily when calculating the delay from clocking a register to a combinatorial output through registered feedback , as shown above. It contains 64 bits of reprogrammable memory that can contain user defined data. Some uses include user ID codes, revision numbers, or inventory control. The signature data is always available to the user independent of the state of the security cell.

NOTE: The electronic signature is included in checksum calculations. Changing the electronic signature will alter the checksum. Once programmed, this cell prevents further read access to the functional bits in the device.

This cell can only be erased by re-programming the device, so the original configuration can never be examined once this cell is programmed. The Electronic Signature is always available to the user, regardless of the state of this control cell.

The negative bias minimizes the potential of latch-up caused by negative input undershoots. Additionally, outputs are designed with n-channel pull-ups instead of the traditional p-channel pull-ups in order to eliminate latch-up due to output overshoots.

This is because, in system operation, certain events occur that may throw the logic into an illegal state power-up, line voltage glitches, brown-outs, etc. To test a design for proper treatment of these conditions, a way must be provided to break the feedback paths, and force any desired i. Then the machine can be sequenced and the outputs tested for correct next state conditions. GAL20V8 devices include circuitry that allows each registered output to be synchronously set either high or low.

Thus, any present state condition can be forced for test sequencing. If necessary, approved GAL programmers capable of executing text vectors perform output register preload automatically. These buffers have a characteristically high impedance, and present a much lighter load to the driving logic than bipolar TTL devices.

Doing this will tend to improve noise immunity and reduce I CC for the device. Complete programming of the device takes only a few seconds. Erasing of the device is transparent to the user, and is done automatically as part of the programming cycle.

As a result, the state on the registered output pins if they are enabled will always be high on power-up, regardless of the programmed polarity of the output pins. This feature can greatly simplify state machine design by providing a known state on power-up. First, the VCC rise must be monotonic. Second, the clock input must be at static TTL level as shown in the diagram during power up. The registers will reset within a maximum of tpr time. As in normal system operation, avoid clocking the device until all input and feedback path setup times have been met.

The clock must also meet the minimum pulse width requirements. C 0 0. C 0 25 50 75 Temperature deg. C 0. Short-link Link Embed. Share from cover. Share from page:. More magazines by this user. Close Flag as Inappropriate. You have already flagged this document. Thank you, for helping us keep this platform clean. The editors will have a look at it as soon as possible.

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