1. Erasable Programmable Logic Devices (EPLDs)
EP300 is the first member of EPLD introduced by the Altera.
It is a 20 pin IC and operates with a clock frequency of 18MHz.
It has 18 inputs and 3 outputs.
It consists 8 macrocells and each of which has 9 product terms.
8 product terms are feed to an 8 input OR gate and the remaining term is used to enable the output

2. Altera MAX 7000 series CPLD

3. EP300 Macrocell

4. It consists output multiplexer and feedback multiplexer.
EP300 Macrocell
It consists output multiplexer and feedback multiplexer.
The output multiplexer allows the selection of the direct output of the OR gate or the registered output or their complements.
The feedback multiplexer allows the feedback from the output of OR gate, the output of the register or from the bidirectional I/O pin.
EP300 has 2 additional product terms used for register set and reset functions.
When the preset input is asserted high, the register is loaded with logic ‘1’ on the positive edge of the clock pulse.

5. EP310 is operates with a maximum clock frequency of 40MHz.
EP300 Macrocell
If the clear input is asserted high, the register is loaded with logic ‘0’ independent of the clock pulse.
EP310 is operates with a maximum clock frequency of 40MHz.
EP310 requires less power than EP300.
Both EP300 and EP310 has a security bit that prevents unauthorized reading of data programmed into the device.

6. Each I/O pin can provide either combinational or registered output.
EP320
The output of the OR gate in EP320 is fed to the input of the corresponding register via an EX-OR gate, whereas in EP300/EP310 the output of the OR gate is fed directly to the register input.
Each I/O pin can provide either combinational or registered output.
In each mode, output polarity is selected by setting the unused input of the EX-OR gate appropriately (logic “1” for active-low, logic “0” for active-high).
In both combinational and registered modes, there is an option for feedback or no feedback of output.

7. It has 10 dedicated inputs, one of which may be used as a clock input.
EP320
It has 10 dedicated inputs, one of which may be used as a clock input.
The device also has 8 I/O pins which may be used as inputs or outputs depending on the OE product term is asserted low or high, respectively.
It has 8 separate OE product terms, thus it is possible to individually enable or disable each output as in EP300/EP310.
EP320 does not have dedicated product terms for preset and clear operations.

8. EP320 Combinational and Register Output Modes