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Lattice Semiconductor
87
Data Sheet
November 2006
ORCA Series 3C and 3T FPGAs
Conguration Data Format
The ispLEVER Development System interfaces with
front-end design entry tools and provides tools to pro-
duce a fully congured FPGA. This section discusses
using the ispLEVER Development System to generate
conguration RAM data and then provides the details
of the conguration frame format.
The
ORCA OR3Cxx and OR3Txxx Series FPGAs are
bit stream compatible.
Using ispLEVER to Generate
Conguration RAM Data
The conguration data bit stream denes the I/O func-
tionality, logic, and interconnections within the FPGA.
The bit stream is generated by the development sys-
tem. The bit stream created by the bit stream genera-
tion tool is a series of 1s and 0s used to write the FPGA
conguration RAM. It can be loaded into the FPGA
using one of the conguration modes discussed later.
In the bit stream generator, the designer selects
options that affect the FPGA’s functionality. Using the
output of the bit stream generator, circuit_name.bit,
the development system’s download tool can load the
conguration data into the
ORCA series FPGA evalua-
tion board from a PC or workstation.
Alternatively, a user can program a PROM (such as a
Serial ROM or a standard EPROM) and load the FPGA
from the PROM. The development system’s PROM
programming tool produces a le in .mks or .exo for-
mat.
Conguration Data Frame
Conguration data can be presented to the FPGA in
two frame formats: autoincrement and explicit. A
detailed description of the frame formats is shown in
Figure 52, Figure 53, and
Table 32. The two modes are
similar except that autoincrement mode uses assumed
address incrementation to reduce the bit stream size,
and explicit mode requires an address for each data
frame. In both cases, the header frame begins with a
series of 1s and a preamble of 0010, followed by a
24-bit length count eld representing the total number
of conguration clocks needed to complete the loading
of the FPGAs.
Following the header frame is a mandatory ID frame.
(Note that the ID frame was optional in the
ORCA 2C
and 2C/TxxA Series.)
The ID frame contains data used to determine if the bit
stream is being loaded to the correct type of
ORCA
FPGA (i.e., a bit stream generated for an OR3T55 is
being sent to an OR3T55). Error checking is always
enabled for Series 3 devices, through the use of an
8-bit checksum. One bit in the ID frame also selects
between the autoincrement and explicit address modes
for this load of the conguration data.
A conguration data frame follows the ID frame. A data
frame starts with a 01-start bit pair and ends with
enough 1-stop bits to reach a byte boundary. If using
autoincrement conguration mode, subsequent data
frames can follow. If using explicit mode, one or more
address frames must follow each data frame, telling the
FPGA at what addresses the preceding data frame is
to be stored (each data frame can be sent to multiple
addresses).
Following all data and address frames is the postam-
ble. The format of the postamble is the same as an
address frame with the highest possible address value
with the checksum set to all ones.
Select
devices
have
been
discontinued.
See
Ordering
Information
section
for
product
status.