IGLOO Low-Power Flash FPGAs with Flash*Freeze Technology
A d v an c ed v0 . 1
2-59
Actel recommends that VPUMP and VJTAG power supplies
are kept separate with independent filtering capacitors
rather than supplying them from a common rail.
User Pins
I/O
User Input/Output
The I/O pin functions as an input, output, tristate, or
bidirectional buffer. Input and output signal levels are
compatible with the I/O standard selected.
During programming, I/Os become tristated and weakly
pulled up to VCCI. With VCCI, VMV, and VCC supplies
continuously powered up, when the device transitions
from programming to operating mode, the I/Os are
instantly configured to the desired user configuration.
Unused I/Os are configured as follows:
Output buffer is disabled (with tristate value of high
impedance).
Input buffer is disabled (with tristate value of high
impedance).
Weak pull-up is programmed.
GL
Globals
GL I/Os have access to certain clock conditioning circuitry
(and the PLL) and/or have direct access to the global
network (spines). Additionally, the global I/Os can be
used as I/Os, since they have identical capabilities.
Unused GL pins are configured as inputs with pull-up
resistors. See more detailed descriptions of global I/O
into the quadrant clocks. For example, if GAA0 is used
for an input, GAA1 and GAA2 are no longer available for
input to the quadrant globals. All inputs labeled GC/GF
are direct input into the chip-level globals, and the rest
are connected to the quadrant globals. The inputs to the
global network are multiplexed, and only one input can
be used as a global input.
page 2-56 for an explanation of the naming of global
pins.
FF
Flash*Freeze Mode Activation Pin
The FF pin is a dedicated input pin that is used to enter
and exit Flash*Freeze mode. The FF pin is active low, has
the same characteristics as a single-ended I/O, and must
meet
the
maximum
rise
and
fall
time.
When
Flash*Freeze mode is not used in the design, the FF pin is
available as a regular I/O.
When Flash*Freeze mode is used, the FF pin must not be
left floating to avoid accidentally entering Flash*Freeze
mode. While in Flash*Freeze mode, the Flash*Freeze pin
should be constantly asserted.
The Flash*Freeze pin can be used with any single-ended
I/O standard supported by the I/O bank in which the pin
is located, and input signal levels compatible with the I/O
standard selected. The FF pin should be treated as a
sensitive
asynchronous
signal.
When
defining
pin
placement and board layout, simultaneously switching
outputs
(SSOs)
and
their
effects
on
sensitive
asynchronous pins must be considered.
Unused FF or I/O pins are tristated with weak pull-up.
This default configuration applies to both Flash*Freeze
mode and normal operation mode. No user intervention
is required.
Table 2-32 shows the Flash*Freeze pin location on the
available packages for IGLOO devices. The Flash*Freeze
pin
location
is
independent
of
device,
allowing
migration to larger or smaller IGLOO devices while
maintaining the same pin location on the board.
Table 2-32 Flash*Freeze Pin Location in IGLOO Family
Packages (device-independent)
Package
Flash*Freeze Pin
CS196
TBD
QN132
B12
VQ100
27
FG144
L3
FG256
T3
FG484
W6