AN1096 Datasheet PDF - Microchip
Part Number | AN1096 | |
Description | Using the C30 Compiler to Interface SPI Serial EEPROMs | |
Manufacturers | Microchip | |
Logo | ||
There is a preview and AN1096 download ( pdf file ) link at the bottom of this page. Total 12 Pages |
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Using the C30 Compiler to Interface SPI Serial EEPROMs
with dsPIC33F and PIC24F
Author: Martin Kvasnicka
Microchip Technology Inc.
INTRODUCTION
The 25XXX series serial EEPROMs from Microchip
Technology are SPI compatible and have maximum
clock frequencies ranging from 3 MHz to 20 MHz. Many
times when designing an application which utilizes a
serial EEPROM device, it may be beneficial to use a
microcontroller which does not feature a dedicated
protocol-specific serial port. This can be due to several
possible reasons, including size restrictions or costs. In
these instances, it is required of the designer to write
software routines capable of generating the proper
signals for communicating with the EEPROM device.
This application note provides assistance and source
code to ease the design process of interfacing a
Microchip dsPIC33F Digital Signal Controller to a
Microchip SPI serial EEPROM, without the use of a
hardware serial port.
Figure 1 describes the hardware schematic for the
interface between Microchip’s 25XXX series devices
and the dsPIC33F DSC or PIC24F PIC® microcontrol-
ler. The schematic shows the connections necessary
between the DSC or PIC MCU and the serial EEPROM
as tested, and the software was written assuming
these connections. The WP and HOLD pins are tied to
VCC through resistors, because the write-protect and
hold features are not used in the examples provided.
FIGURE 1:
CIRCUIT FOR dsPIC33F256GP710, PIC24FJ128GA010 AND 25XXX SERIES
DEVICES
100 Pin TQFP
dsPIC33FJ256GP710
PIC24FJ128GA010
SDA1/RG3
SCK1/INT0/RF6
SDI1/RF7
SDO1/RF8
U1RX/RF2
U1TX/RF3
CS 1
SO 2
WP 3
Vss 4
Vcc
8 Vcc
7 HOLD
6 SCK
5 SI
Note: CS, WP and HOLD pins should all have pull-up resistors (~10k-ohms).
© 2007 Microchip Technology Inc.
DS01096B-page 1
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AN1096
BYTE WRITE COMMAND (OPCODE,
ADDRESS AND DATA)
Figure 4 shows an example of the Write command.
First, the device is selected by bringing Chip Select low
(active). In this example, the Most Significant bit of the
address is a ‘1’. This bit is embedded in the opcode
(0x02 for a Write command), and so the value, 0x0A, is
sent. The Low Address byte (0x33) is sent next. Finally,
the data is clocked in, in this case, 0xCC. Once Chip
Select is toggled at the end of this command, the inter-
nal write cycle is initiated. After the write cycle has
begun, the WIP bit in the STATUS register can be
polled to check when the write finishes. If polling is not
used, a delay (~5ms) needs to be added to ensure the
write has finished. This code uses WIP polling.
A page write can be accomplished by continuing to
send data bytes to the device without toggling CS. Up
to 16 bytes can be written to the 25LC040A before a
write cycle is needed. Once CS is brought high after the
data bytes have been transmitted, then the write cycle
timer will begin and normal polling can be initiated.
The Page Write function provided in the firmware is
used to program 16 bytes of data, starting at address
0x150. Because page writes cannot cross page bound-
aries, care must be taken to avoid having data wrap
around to the beginning of the page and overwrite
existing data.
FIGURE 4:
BYTE WRITE COMMAND, ADDRESS AND DATA
CS
SCK
SI
SO
TWC
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Instruction
Low Address Byte
Data Byte
0 0 0 0 A8 0 1 0 A7 A6 A5 A4 A3 A2 A1 A0 7 6 5 4 3 2 1 0
High-Impedance
© 2007 Microchip Technology Inc.
DS01096B-page 5
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Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for AN1096 electronic component. |
Information | Total 12 Pages | |
Link URL | [ Copy URL to Clipboard ] | |
Download | [ AN1096.PDF Datasheet ] |
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