I/O Structures in IGLOO and ProASIC3 Devices
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I/O Bank Structure
Low-power flash device I/Os are divided into multiple technology banks. The number of banks is
device-dependent. The IGLOOe, ProASIC3EL, and ProASIC3E devices have eight banks (two per
side); and IGLOO, ProASIC3L, and ProASIC3 devices have two to four banks. Each bank has its own
VCCI power supply pin. Multiple I/O standards can co-exist within a single I/O bank.
In IGLOOe, ProASIC3EL, and ProASIC3E devices, each I/O bank is subdivided into VREF minibanks.
These are used by voltage-referenced I/Os. VREF minibanks contain 8 to 18 I/Os. All I/Os in a given
minibank share a common VREF line (only one VREF pin is needed per VREF minibank). Therefore, if
an I/O in a VREF minibank is configured as a VREF pin, the remaining I/Os in that minibank will be
able to use the voltage assigned to that pin. If the location of the VREF pin is selected manually in
Devices). If the user does not pick the VREF pin manually, the software automatically assigns the VREF pin.
Figure 7-3 is a snapshot of a section of the I/O ring, showing the basic elements of an I/O tile, as
viewed from the Designer place-and-route tool’s MultiView Navigator (MVN).
Low-power flash device I/Os are implemented using two tile types: I/O and differential I/O (diffio).
The diffio tile is built up using two I/O tiles, which form an I/O pair (P side and N side). These I/O
pairs are used according to differential I/O standards. Both the P and N sides of the diffio tile
include an I/O buffer and two I/O logic blocks (auxiliary and main logic).
Every minibank (E devices only) is built up from multiple diffio tiles. The number of the minibank
illustration of the minibank structure.
signal (OE) enables the output buffer to pass the signal from the core logic to the pin. The output
buffer contains ESD protection circuitry, an n-channel transistor that shunts all ESD surges (up to
the limit of the device ESD specification) to GND. This transistor also serves as an output pull-down
resistor.
Each output buffer also contains programmable slew rate, drive strength, programmable power-up
state (pull-up/-down resistor), hot-swap, 5 V tolerance, and clamp diode control circuitry. Multiple
software to activate different I/O features.
Figure 7-3 Snapshot of an I/O Tile
{
I/O Pad/Buffer I/O Logic (assigned)
N Side
(assigned)
P Side
(unassigned)
Diffio Tile
Minibank
Other
Minibanks