I/O Structures in IGLOOe and ProASIC3E Devices

34

v1.4

Board-Level Considerations

Low-power flash devices have robust I/O features that can help in reducing board-level

components. The devices offer single-chip solutions, which makes the board layout simpler and

more immune to signal integrity issues. Although, in many cases, these devices resolve board-level

issues, special attention should always be given to overall signal integrity. This section covers

important board-level considerations to facilitate optimum device performance.

Termination

Proper termination of all signals is essential for good signal quality. Nonterminated signals,

especially clock signals, can cause malfunctioning of the device.

For general termination guidelines, refer to the Board-Level Considerations application note for

Actel FPGAs. Also refer to Pin Descriptions for termination requirements for specific pins.

Low-power flash I/Os are equipped with on-chip pull-up/-down resistors. The user can enable these

resistors by instantiating them either in the top level of the design (refer to the IGLOO, Fusion, and

ProASIC3 Macro Library Guide for the available I/O macros with pull-up/-down) or in the I/O

Attribute Editor in Designer if generic input or output buffers are instantiated in the top level.

Unused I/O pins are configured as inputs with pull-up resistors.

As mentioned earlier, low-power flash devices have multiple programmable drive strengths, and

the user can eliminate unwanted overshoot and undershoot by adjusting the drive strengths.

Figure 20 • User I/O Naming Conventions of IGLOOe and ProASIC3E Devices – Top View

GNDQ

VMV7

VMV6

GNDQ

V

CC

V

CC

V

COMPLF

V

CCPLF

V

COMPLE

V

CCPLE

V

COMPLA

V

CCPLA

GND

V

V

GND

V

CC

GNDQ

VMV2

GND

TRST

TDO

VMV3

GNDQ

V

COMPLB

V

COMPLC

V

CCPLB

V

CCPLC

V

JTAG

V

CC

V

CC

V

COMPLD

V

PUMP

V

CCPLD

V

GND

V

CC

V

CCIB3

CCC/PLL

“D”

Bank 5

Bank 4

JTAG

AGLE600/A3PE600

A3PE1500

AGLE3000A3PE3000

Bank 0

Bank 1

CCC/PLL

“C”

CCC/PLL

“B”

CCC/PLL

“E”

CCC/PLL

“F”

CCC/PLL

“A”