參數(shù)資料
型號: OR4E10
廠商: Lineage Power
英文描述: Field-Programmable Gate Arrays(現(xiàn)場可編程門陣列)
中文描述: 現(xiàn)場可編程門陣列(現(xiàn)場可編程門陣列)
文件頁數(shù): 64/132頁
文件大?。?/td> 2667K
代理商: OR4E10
64
Lucent Technologies Inc.
Preliminary Data Sheet
August 2000
ORCA Series 4 FPGAs
FPGA Configuration Modes
(continued)
In master parallel mode, the starting memory address
is 00000 hex, and the FPGA increments the address
for each byte loaded.
One master mode FPGA can interface to the memory
and provide configuration data on DOUT to additional
FPGAs in a daisy-chain. The configuration data on
DOUT is provided synchronously with the falling edge
of CCLK. The frequency of the CCLK output is eight
times that of RCLK.
Master Serial Mode
In the master serial mode, the FPGA loads the configu-
ration data from an external serial ROM. The configura-
tion data is either loaded automatically at start-up or on
a
PRGM
command to reconfigure. Serial PROMs can
be used to configure the FPGA in the master serial
mode.
Configuration in the master serial mode can be done at
powerup and/or upon a configure command. The sys-
tem or the FPGA must activate the serial ROM's
RESET
/OE and
CE
inputs. At powerup, the FPGA and
serial ROM each contain internal power-on reset cir-
cuitry that allows the FPGA to be configured without
the system providing an external signal. The power-on
reset circuitry causes the serial ROM's internal address
pointer to be reset. After powerup, the FPGA automati-
cally enters its initialization phase.
The serial ROM/FPGA interface used depends on such
factors as the availability of a system reset pulse, avail-
ability of an intelligent host to generate a configure
command, whether a single serial ROM is used or mul-
tiple serial ROMs are cascaded, whether the serial
ROM contains a single or multiple configuration pro-
grams, etc. Because of differing system requirements
and capabilities, a single FPGA/serial ROM interface is
generally not appropriate for all applications.
Data is read in the FPGA sequentially from the serial
ROM. The DATA output from the serial ROM is con-
nected directly into the DIN input of the FPGA. The
CCLK output from the FPGA is connected to the CLK
input of the serial ROM. During the configuration pro-
cess, CCLK clocks one data bit on each rising edge.
Since the data and clock are direct connects, the
FPGA/serial ROM design task is to use the system or
FPGA to enable the
RESET
/OE and
CE
of the serial
ROM(s). There are several methods for enabling the
serial ROM’s
RESET
/OE and
CE
inputs. The serial
ROM’s
RESET
/OE is programmable to function with
RESET active-high and
OE
active-low or
RESET
active-
low and OE active-high.
In Figure 39, serial ROMs are cascaded to configure
multiple daisy-chained FPGAs. The host generates a
500 ns low pulse into the FPGA's
PRGM
input. The
FPGA’s
INIT
input is connected to the serial ROMs’
RESET
/OE input, which has been programmed to
function with
RESET
active-low and OE active-high.
The FPGA DONE is routed to the
CE
pin. The low on
DONE enables the serial ROMs. At the completion of
configuration, the high on the FPGA’s DONE disables
the serial ROM.
Serial ROMs can also be cascaded to support the con-
figuration of multiple FPGAs or to load a single FPGA
when configuration data requirements exceed the
capacity of a single serial ROM. After the last bit from
the first serial ROM is read, the serial ROM outputs
CEO
low and 3-states the DATA output. The next serial
ROM recognizes the low on
CE
input and outputs con-
figuration data on the DATA output. After configuration
is complete, the FPGA’s DONE output into
CE
disables
the serial ROMs.
This FPGA/serial ROM interface is not used in applica-
tions in which a serial ROM stores multiple configura-
tion programs. In these applications, the next
configuration program to be loaded is stored at the
ROM location that follows the last address for the previ-
ous configuration program. The reason the interface in
Figure 39 will not work in this application is that the low
output on the
INIT
signal would reset the serial ROM
address pointer, causing the first configuration to be
reloaded.
In some applications, there can be contention on the
FPGA's DIN pin. During configuration, DIN receives
configuration data, and after configuration, it is a user
I/O. If there is contention, an early DONE at start-up
(selected in ORCA Foundry) may correct the problem.
An alternative is to use
LDC
to drive the serial ROM's
CE
pin. In order to reduce noise, it is generally better to
run the master serial configuration at 1.25 MHz (M3 pin
tied high), rather than 10 MHz, if possible.
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