Digilent PmodSF™ 16Mbit SPI
Serial Flash Memory Module
Reference Manual
Revision: September 26, 2006
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Overview
The Digilent PmodSF is a Digilent Pmod
TM
peripheral module that provides 16Mbit
(2Mbyte) of flash ROM memory. This memory
is accessed through an SPI (Serial Peripheral
Interface) compatible serial interface. This
module provides easily accessible non-volatile
memory storage for various Digilent
programmable logic and embedded control
system boards.
Features include:
•
•
•
•
•
ST Microelectronics M25P16 serial
flash ROM integrated circuit
a 6-pin header Pmod interface
connector
more than 20 year data retention
very low power consumption
small form factor (0.80” x 1.00”).
Figure 1
Digilent PmodSF
1 SS
2 MOSI
3 MISO
J1 Connector
4 SCK
S
D
Q
C
Serial
Flash
ROM
M25P16
5 GND
Functional Description
6 VCC
The flash memory on the PmodSF is provided
by an ST Microelectronics M25P16 integrated
circuit. This memory is organized as 32 sectors
of 65536 (64K) bytes each. Each sector is
organized as 256 pages of 256 bytes each.
Flash memory must be erased before new
data can be written. The M25P16 allows for a
bulk erase, to erase the entire memory, or
individual sectors may be erased
independently. After a sector has been erased,
individual bytes within the sector can be written
or complete pages may be written as a single
write operation.
Flash memory will eventually wear out after
many erase reprogram cycles. The M25P16
supports more than 100,000 erase/program
cycles per sector before the memory wears
out. Normally flash memory wear-out is not an
Doc: 502-103
Figure 2
Block Diagram
issue in routine operation. However, be aware
that bugs in the control software may
inadvertently cause many erase/program
cycles to happen quickly. This could result in
premature wear-out of the memory.
Sending commands and data to the module via
the SPI interface accesses the flash memory
on the PmodSF.
The SPI interface standard uses four signal
lines. These are SS, slave select; MOSI,
master out slave in; MISO, master in slave out;
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and SCK, serial clock. These signals map to
the following signals on the M25P16 flash
ROM part as described in the ST
Microelectronics data sheet: SS corresponds
to the Chip Select signal, S; MOSI corresponds
to Serial Data Input, D; MISO corresponds to
Serial Data Output, Q; and SCK corresponds
to the Serial Clock signal, C. See Table 1 for a
description of the pins on Pmod interface
connector J1.
The M25P16 flash ROM IC provides additional
inputs called “Hold” and “Write Protect” that are
not used on the PmodSF module. These
signals are held in the inactive state on the
module.
A system board interacts with the PmodSF
module by sending commands over the SPI
interface. Depending on the command sent,
the system board will then send memory data
to, or receive memory data from, the module.
The M25P16 provides commands to perform
sector erase, bulk erase, page program, and
write commands as well as other
miscellaneous commands. Please refer to the
ST Microelectronics data sheet for the M25P16
IC for detailed information on the operation of
this integrated circuit.
The PmodSF is designed to work with either
Digilent programmable logic or Digilent
embedded control system boards. Some
system boards, such as the Nexys, Basys and
Cerebot boards, have 6-pin header connectors
into which the PmodSF will connect directly.
Other Digilent system boards may need a
Digilent Module Interface Board (MIB) and a 6-
pin cable to connect to the PmodSF. The MIB
plugs into the system board and the cable
connects the MIB to the PmodSF.
The PmodSF requires a 3.3V supply voltage.
This power supply voltage is available on all
Digilent system boards and is provided as part
of the 6-wire Pmod interface standard. Digilent
system boards that provide Pmod interface
connectors, allow jumper selection of the
power supply voltage being provided to the
Pmod. Ensure that the system board is
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jumpered to provide 3.3V to the module before
applying power to the board.
For detailed information on the M25P16, see
the ST Microelectronics data sheet available at
www.st.com.
Table 1: Connector J1 Signals
Pin
Signal
1
SS (S)
2
MOSI (D)
3
MISO (Q)
4
SCK (C)
5
GND
6
VCC
Copyright Digilent, Inc.
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