Spartan-3E FPGA Family: Functional Description
DS312 (v4.1) July 19, 2013
Product Specification
83
Daisy-Chaining
If the application requires multiple FPGAs with different
configurations, then configure the FPGAs using a daisy
chain, as shown in
Figure 57. Daisy-chaining from a single
SPI serial Flash PROM is supported in Stepping 1 devices.
It is not supported in Stepping 0 devices. Use SPI Flash
mode (M[2:0] = <0:0:1>) for the FPGA connected to the
Platform Flash PROM and Slave Serial mode
(M[2:0] = <1:1:1>) for all other FPGAs in the daisy-chain.
After the master FPGA—the FPGA on the left in the
diagram—finishes loading its configuration data from the
SPI Flash PROM, the master device uses its DOUT output
pin to supply data to the next device in the daisy-chain, on
the falling CCLK edge.
Design Note
SPI mode daisy chains are supported only in Stepping 1
silicon versions.
Programming Support
For successful daisy-chaining, the DONE_cycle
configuration option must be set to cycle 5 or sooner. The
additional information.
In production applications, the SPI Flash PROM is
usually pre-programmed before it is mounted on the printed
produces industry-standard programming files that can be
used with third-party gang programmers. Consult your
specific SPI Flash vendor for recommended production
programming solutions.
In-system programming support is available from some
third-party PROM programmers using a socket adapter with
attached wires. To gain access to the SPI Flash signals,
drive the FPGA’s PROG_B input Low with an open-drain
driver. This action places all FPGA I/O pins, including those
attached to the SPI Flash, in high-impedance (Hi-Z). If the
HSWAP input is Low, the I/Os have pull-up resistors to the
VCCO input on their respective I/O bank. The external
programming hardware then has direct access to the SPI
Flash pins. The programming access points are highlighted
Beginning with the Xilinx ISE 8.2i software release, the
iMPACT programming utility provides direct, in-system
prototype programming support for STMicro M25P-series
X-Ref Target - Figure 57
Figure 57: Daisy-Chaining from SPI Flash Mode (Stepping 1)
+2.5V
TDI
TDO
TMS
TCK
VCCINT
VCCAUX
+2.5V
CSO_B
VCCO_2
INIT_B
DIN
MOSI
PROG_B
DONE
GND
+1.2V
DATA_IN
SELECT
VCC
DATA_OUT
CLOCK
GND
HSWAP
VCCO_0
P
CCLK
TDI
TDO
TMS
TCK
VCCINT
VCCAUX
DIN
DOUT
VCCO_2
INIT_B
PROG_B
DONE
GND
+1.2V
M2
M1
‘1’
M0
HSWAP
VCCO_0
P
+3.3V
+2.5V
‘1’
VCCO_0
4.
7k
Slave
Serial
Mode
+2.5V
JTAG
CCLK
INIT_B
DONE
PROG_B
TCK
TMS
SPI
Serial
Flash
PROG_B
Recommend
open-drain
driver
VCCO_0
TDI
TMS
TCK
TDO
+3.3V
HOLD
‘1’
M2
M1
‘0’
M0
SPI Mode
‘1’
VS2
VS1
‘1’
VS0
Variant Select
‘1’
S
DOUT
Spartan-3E
FPGA
Spartan-3E
FPGA
DOUT
CCLK
WR_PROTECT
W
+3.3V
P
4.
7k
33
0
I
4.
7
k
DS312-2_48_082009
!
SPI-based daisy-chaining is
only supported in Stepping 1.
I