U3280M Datasheet, PDF (7/18 Pages) ATMEL Corporation – TRANSPONDER INTERFACE FOR MICROCONTROLLER

Figure 6. Serial Protocol
SCL
U3280M
EEPROM
EEPROM Operating
Modes
SDA
Stand- _START
by condition
Data
valid
Data Data/
change acknowledge
valid
STOP Stand-
condition by
Control Byte Format
START A4
EEPROM address
A3
A2
A1
Mode control
bits
Read/
NWrite
A0
C1
C0
R/NW Ackn
The control byte follows the START condition and consists of the 5-bit row address, 2
mode control bits and the read/not-write bit.
Data Transfer Sequence
START Control byte Ackn
Data byte
Ackn
Data byte
Ackn
STOP
• After the STOP condition and before the START condition the device is in standby
mode and the SDA line is switched to an input with the pull-up resistor.
• The START condition follows a control byte that determines the following operation.
Bit 0 of the control byte is used to control the following transfer direction. A “0”
defines a write access and a “1” defines a read access.
The EEPROM has a size of 512 bits and is organized as a 32 × 16-bit matrix. To read
and write data to and from the EEPROM, the serial interface must be used. The inter-
face supports one and two-byte write access and one to n-byte read access to the
EEPROM.
The operating modes of the EEPROM are defined by the control byte. The control byte
contains the row address, the mode control bits and the read/not-write bit that is used to
control the direction of the following transfer. A “0” defines the write access and a “1”
defines a read access. The five address bits select one of the 32 rows of EEPROM
memory to be accessed. For complete access the complete 16-bit word of the selected
row is loaded into a buffer. The buffer must be read or overwritten via the serial inter-
face. The two mode control bits C1 and C2 define in which order the access to the buffer
is performed: high byte – low byte or low byte – high byte. The EEPROM also supports
auto-increment and auto-decrement read operations. After sending the START address
with the corresponding mode, consecutive memory cells can be read row by row without
transmission of the row addresses.
Two special control bytes allow the initialization of the complete EEPROM with “0” or
with “1”.
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4688B–RFID–12/04