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Chapter 12: SPI Serial Flash
Other SPI Flash Control Signals
The M25P16 SPI Flash has two additional control inputs. The active-Low write protect
input (W) and the active-Low bus hold input (HLD) are unused and pulled High via an
external pull-up resistor.
Variant Select Pins, VS[2:0]
When in SPI configuration mode, the FPGA samples the value on three pins, labeled
VS[2:0], to determine which SPI read command to issue to the SPI Flash. For the M25P16
Flash, VS[2:0]=<1:1:1> issues the correct command sequence. The VS[2:0] pins are pulled
High externally via pull-up resistors to 3.3V. The VS[2:0] pins are also parallel NOR Flash
address lines A[19:17] in the FPGA's BPI configuration mode and these signals also
connect to the StrataFlash parallel Flash PROM. After SPI configuration, the VS[2:0] pins
become user-programmable I/O pins, allowing full access to the StrataFlash PROM,
despite that the FPGA configured from SPI Flash.
Jumper Block J11
In SPI configuration mode, the FPGA selects the attached SPI Flash by asserting the CSO_B
pin Low. On the Spartan-3E Starter Kit board, the CSO_B pin drives into the jumper J11
block. This jumper block provides the option to move the on-board SPI Flash to a different
select line (SPI_ALT_CS_JP11). This way, a different SPI Flash device can be tested by
changing the JP11 jumper settings and connecting the alternate SPI Flash on Header JP12.
By default, both jumpers are inserted on jumper block header J11.
Programming Header J12
As shown in
to program the on-board SPI Flash.
Multi-Package Layout
STMicroelectronics was rather clever when they defined the package layout for the
M25Pxx SPI serial Flash family. The Spartan-3E Starter Kit board supports all three of the
package types used for the 16 Mbit device, as shown in
ships with the 8-lead, 8x6 mm MLP package. The multi-package layout also supports the 8-
pin SOIC package and the 16-pin SOIC package. Pin 1 for the 8-pin SOIC and MLP
packages is located in the top-left corner. However, pin 1 for the 16-pin SOIC package is
located in the top-right corner, because the package is rotated 90
package also have four pins on each side that do not connect on the board. These pins must
be left floating. Why support multiple packages? In a word, flexibility. The multi-package
layout provides ...
•
•
100
Figure 12-15, page
Density migration between smaller- and larger-density SPI Flash PROMs. Not all
SPI Flash densities are available in all packages. The SPI Flash migration strategy
follows nicely with the pinout migration provided by Xilinx FPGAs.
Consistent configuration PROM layout when migrating between FPGA densities.
The Spartan-3E FPGA's FG320 package footprint supports the XC3S500E, the
XC3S1200E, and the XC3S1600E FPGA devices without modification. The SPI Flash
multi-package layout allows comparable flexibility in the associated configuration
PROM. Ship the optimally-sized SPI Flash memory for the FPGA mounted on the
board.
www.xilinx.com
97, Header J12 accepts a JTAG parallel programming cable
Figure
Spartan-3E Starter Kit Board User Guide
12-19. By default, the board
°
. The 16-pin SOIC
UG230 (v1.0) March 9, 2006
R
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