I/O Structures in IGLOOe and Pro ASIC3E Devices

v1.4

15

I/O Features

Low-power flash devices support multiple I/O features that make board design easier. For example,

an I/O feature like Schmitt Trigger in the ProASIC3E input buffer saves the board space that would

be used by an external Schmitt trigger for a slow or noisy input signal. These features are also

programmable for each I/O, which in turn gives flexibility in interfacing with other components.

The following is a detailed description of all available features in low-power flash devices.

I/O Programmable Features

Low-power flash devices offer many flexible I/O features to support a wide variety of board

designs. Some of the features are programmable, with a range for selection. Table 8 lists

programmable I/O features and their ranges.

Hot-Swap Support

A pull-up clamp diode must not be present in the I/O circuitry if the hot-swap feature is used. The

3.3 V PCI standard requires a pull-up clamp diode on the I/O, so it cannot be selected if hot-swap

capability is required. The A3P030 device does not support 3.3 V PCI, so it is the only device in the

ProASIC3 family that supports the hot-swap feature. All devices in the ProASIC3E family are hot-

swappable. All standards except LVCMOS 2.5/5.0 V and 3.3 V PCI/PCI-X support the hot-swap

feature.

The hot-swap feature appears as a read-only check box in the I/O Attribute Editor that shows

whether an I/O is hot-swappable or not. Refer to Power-Up/-Down Behavior of Low-Power Flash

Devices for details on hot-swapping.

Hot-swapping (also called hot-plugging) is the operation of hot insertion or hot removal of a card

in a powered-up system. The levels of hot-swap support and examples of related applications are

described in Table 9 on page 16 to Table 12 on page 17. The I/Os also need to be configured in hot-

insertion mode if hot-plugging compliance is required. The AGL030 and A3P030 devices have an I/O

structure that allows the support of Level 3 and Level 4 hot-swap with only two levels of staging.

Table 8 • Programmable I/O Features (user control via I/O Attribute Editor)

Feature

Description

Range

Slew Control

Output slew rate

HIGH, LOW

Output Drive (mA)

Output drive strength

2, 4, 6, 8, 12, 16, 24

Skew Control

Output tristate enable delay option

ON, OFF

Resistor Pull

Resistor pull circuit

Up, Down, None

Input Delay

Input delay

OFF, 0–7

Schmitt Trigger

Schmitt trigger for input only

ON, OFF