
Actel Fusion Mixed-Signal FPGAs
Pr el iminar y v1 .7
2- 157
User I/O Naming Convention
Due to the comprehensive and flexible nature of Fusion device user I/Os, a naming scheme is used
name identifies to which I/O bank it belongs, as well as the pairing and pin polarity for differential
I/Os.
I/O Nomenclature
= Gmn/IOuxwByVz
Gmn is only used for I/Os that also have CCC access—i.e., global pins.
G= Global
m
= Global pin location associated with each CCC on the device: A (northwest corner), B (northeast corner), C
(east middle), D (southeast corner), E (southwest corner), and F (west middle).
n
= Global input MUX and pin number of the associated Global location m, either A0, A1, A2, B0, B1, B2, C0,
u
= I/O pair number in the bank, starting at 00 from the northwest I/O bank and proceeding in a clockwise
direction.
x
= P (Positive) or N (Negative) for differential pairs, or R (Regular – single-ended) for the I/Os that support
single-ended and voltage-referenced I/O standards only. U (Positive-LVDS only) or V (Negative-LVDS
only) restrict the I/O differential pair from being selected as an LVPECL pair.
w
= D (Differential Pair), P (Pair), or S (Single-Ended). D (Differential Pair) if both members of the pair are
bonded out to adjacent pins or are separated only by one GND or NC pin; P (Pair) if both members of the
pair are bonded out but do not meet the adjacency requirement; or S (Single-Ended) if the I/O pair is not
bonded out. For Differential (D) pairs, adjacency for ball grid packages means only vertical or horizontal.
Diagonal adjacency does not meet the requirements for a true differential pair.
B
= Bank
y
= Bank number (0–3). The Bank number starts at 0 from the northwest I/O bank and proceeds in a
clockwise direction.
V
= Reference voltage
z
= Minibank number