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HighWire HW400c/2 User Reference Guide Rev 1.0
4.2.28 EEPROM Data Registers (EDR0 – EDR1)
The y are used for holding
bac ading EDR0-1. They are written to the EEPROM during a write operation.
ope
sign
Ta
R i
EEPROM Data Registers are Read/Write registers. The
data bytes to be read from or written to the serial EEPROM.
Values written to EDR0-1 are stored in an internal shift register and cannot be read
k by re
Reading EDR0-1 returns serial data obtained from the most recent EEPROM ERD
ration.
All read/write operations are 2-bytes, since the EEPROM is organized in a x16
format. EDR0 is the least significant data byte (LSB) and EDR1 is the most
ificant data byte (MSB).
ble 58. EEPROM Data Registers (EDRn) Offset Address 0x2A-0x2B
eg ster Offset Byte
EDR0 0x2A LSB
EDR1 0x2B MSB
4.3 Accessing the Serial EEPROM
with
4.3.1 Reading a
Register (EAR, see Section 4.2.25) to the desired word
data is ready – proceed to the next step.
E. Read the data bytes from the EEPROM Data Registers EDR0 (LSB) and EDR1
for the register description.
The serial EEPROM (Atmel AT93C66A and other manufacturers) is organized
256 words of 2 bytes each. One word address is accessed per operation using the
CPLD state machine.
n EEPROM Address
A. Set to EEPROM Address
address.
B. Check the EBSY flag in the EEPROM Operation/Status Register (EOSR, see
Section 4.2.26). If set to “0”, proceed to the next step.
C. Write a “0x08” to the EOSR. This starts the read operation, which typically
takes 35 us to complete.
. Check the EBSY flag. If set to “0”, the D
(MSB). See section 4.2.27
October 10, 2006 Copyright 2006, SBE, Inc. Page 63