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Lucent Technologies Inc.
Preliminary Data Sheet, Rev. 1
ORCA Series 3 FPGAs
September 1998
Special Function Blocks (continued)
The readback frame contains the configuration data
and the state of the internal logic. During readback, the
value of all registered PFU and PIC outputs can be
captured. The following options are allowed when
doing a capture of the PFU outputs.
1. Do not capture data (the data written to the RAMs,
usually 0, will be read back).
2. Capture data upon entering readback.
3. Capture data based upon a configurable signal
internal to the FPGA. If this signal is tied to
logic 0, capture RAMs are written continuously.
4. Capture data on either options 2 or 3 above.
The readback frame has an identical format to that of
the configuration data frame, which is discussed later
in the Configuration Data Format section. If LUT mem-
ory is not used as RAM and there is no data capture,
the readback data (not just the format) will be identical
to the configuration data for the same frame. This
eases a bitwise comparison between the configuration
and readback data. The configuration header, including
the length count field, is not part of the readback frame.
The readback frame contains bits in locations not used
in the configuration. These locations need to be
masked out when comparing the configuration and
readback frames. The development system optionally
provides a readback bit stream to compare to readback
data from the FPGA. Also note that if any of the LUTs
are used as RAM and new data is written to them,
these bits will not have the same values as the original
configuration data frame either.
Global 3-State Control (TS_ALL)
To increase the testability of the
ORCA Series FPGAs,
the global 3-state function (TS_ALL) disables the
device. The TS_ALL signal is driven from either an
external pin or an internal signal. Before and during
configuration, the TS_ALL signal is driven by the input
pad RD_CFG. After configuration, the TS_ALL signal
can be disabled, driven from the RD_CFG input pad, or
driven by a general routing signal in the upper right cor-
ner. Before configuration, TS_ALL is active-low; after
configuration, the sense of TS_ALL can be inverted.
The following occur when TS_ALL is activated:
1. All of the user I/O output buffers are 3-stated, the
user I/O input buffers are pulled up (with the pull-
down disabled), and the input buffers are configured
with TTL input thresholds (OR3Cxx only).
2. The TDO/RD_DATA output buffer is 3-stated.
3. The RD_CFG, RESET, and PRGM input buffers remain
active with a pull-up.
4. The DONE output buffer is 3-stated, and the input
buffer is pulled up.
Internal Oscillator
The internal oscillator resides in the lower left corner of
the FPGA array. It has output clock frequencies of
1.25 MHz and 10 MHz. The internal oscillator is the
source of the internal CCLK used for configuration. It
may also be used after configuration as a general-
purpose clock signal.
Global Set/Reset (GSRN)
The GSRN logic resides in the lower right corner of the
FPGA. GSRN is an invertible, default, active-low signal
that is used to reset all of the user-accessible latches/
FFs on the device. GSRN is automatically asserted at
powerup and during configuration of the device.
The timing of the release of GSRN at the end of config-
uration can be programmed in the start-up logic
described below. Following configuration, GSRN may
be connected to the RESET pin via dedicated routing, or
it may be connected to any signal via normal routing.
Within each PFU and PIO, individual FFs and latches
can be programmed to either be set or reset when
GSRN is asserted. A new option in Series 3 allows indi-
vidual PFUs and PIOs to turn off the GSRN signal to its
latches/FFs after configuration.
The RESET input pad has a special relationship to
GSRN. During configuration, the RESET input pad
always initiates a configuration abort, as described in
the FPGA States of Operation section. After configura-
tion, the global set/reset signal (GSRN) can either be
disabled (the default), directly connected to the RESET
input pad, or sourced by a lower-right corner signal. If
the RESET input pad is not used as a global reset after
configuration, this pad can be used as a normal input
pad.