FLEX10KA datasheet(39/128 Pages) ALTERA

39 / 128 page

Altera Corporation

FLEX 10K Embedded Programmable Logic Device Family Data Sheet

Slew-Rate Control

The output buffer in each IOE has an adjustable output slew rate that can

be configured for low-noise or high-speed performance. A slower slew

rate reduces system noise and adds a maximum delay of approximately

2.9 ns. The fast slew rate should be used for speed-critical outputs in

systems that are adequately protected against noise. Designers can specify

the slew rate on a pin-by-pin basis during design entry or assign a default

slew rate to all pins on a device-wide basis. The slow slew rate setting

affects only the falling edge of the output.

Open-Drain Output Option

FLEX 10K devices provide an optional open-drain (electrically equivalent

to an open-collector) output for each I/O pin. This open-drain output

enables the device to provide system-level control signals (e.g., interrupt

and write enable signals) that can be asserted by any of several devices. It

can also provide an additional wired-OR plane. Additionally, the Altera

software can convert tri-state buffers with grounded data inputs to open-

drain pins automatically.

Open-drain output pins on FLEX 10K devices (with a pull-up resistor to

the 5.0-V supply) can drive 5.0-V CMOS input pins that require a VIH of

3.5 V. When the open-drain pin is active, it will drive low. When the pin is

inactive, the trace will be pulled up to 5.0 V by the resistor. The open-drain

pin will only drive low or tri-state; it will never drive high. The rise time

is dependent on the value of the pull-up resistor and load impedance. The

IOL current specification should be considered when selecting a pull-up

resistor.

Output pins on 5.0-V FLEX 10K devices with VCCIO = 3.3 V or 5.0 V (with

a pull-up resistor to the 5.0-V supply) can also drive 5.0-V CMOS input

pins. In this case, the pull-up transistor will turn off when the pin voltage

exceeds 3.3 V. Therefore, the pin does not have to be open-drain.

MultiVolt I/O Interface

The FLEX 10K device architecture supports the MultiVolt I/O interface

feature, which allows FLEX 10K devices to interface with systems of

differing supply voltages. These devices have one set of VCC pins for

internal operation and input buffers (VCCINT) and another set for I/O

output drivers (VCCIO).

FLEX10KA датащи(PDF) 39 Page - Altera Corporation