EPF8282AV datasheet(15/62 Pages) ALTERA

15 / 62 page

Altera Corporation

FLEX 8000 Programmable Logic Device Family Data Sheet

Asynchronous Clear

A register is cleared by one of the two LABCTRL signals. When the CLRn

port receives a low signal, the register is set to zero.

Asynchronous Preset

An asynchronous preset is implemented as either an asynchronous load

or an asynchronous clear. If DATA3 is tied to VCC, asserting LABCTRLl

asynchronously loads a 1 into the register. Alternatively, the

MAX+PLUS II software can provide preset control by using the clear and

inverting the input and output of the register. Inversion control is

available for the inputs to both LEs and IOEs. Therefore, if a register is

preset by only one of the two LABCTRL signals, the DATA3 input is not

needed and can be used for one of the LE operating modes.

Asynchronous Clear & Preset

When implementing asynchronous clear and preset, LABCTRL1 controls

the preset and LABCTRL2 controls the clear. The DATA3 input is tied to VCC;

therefore, asserting LABCTRL1 asynchronously loads a 1 into the register,

effectively presetting the register. Asserting LABCTRL2 clears the register.

Asynchronous Load with Clear

When implementing an asynchronous load with the clear, LABCTRL1

implements the asynchronous load of DATA3 by controlling the register

preset and clear. LABCTRL2 implements the clear by controlling the

Asynchronous Load with Preset

When implementing an asynchronous load in conjunction with a preset,

the MAX+PLUS II software provides preset control by using the clear and

inverting the input and output of the register. Asserting LABCTRL2 clears

the register, while asserting LABCTRL1 loads the register. The

MAX+PLUS II software inverts the signal that drives the DATA3 signal to

account for the inversion of the register’s output.

Asynchronous Load without Clear or Preset

When implementing an asynchronous load without the clear or preset,

LABCTRL1

implements the asynchronous load of DATA3 by controlling the

EPF8282AV Datasheet(PDF) 15 Page - Altera Corporation