Data Sheet 71M6531D/F-71M6532D/F
FDS 6531/6532 005
Status
Bit
Read/ Reset
Write State
Name
Polarity Description
3:0
CMD[3:0]
W
0000 Positive
CMD[3:0]
Operation
0000
No-op command. Stops the I2C
clock (SCK, DIO4). If not issued,
SCK keeps toggling.
0010
Receive a byte from the EEPROM
and send ACK.
0011
0101
0110
Transmit a byte to the EEPROM.
Issue a STOP sequence.
Receive the last byte from the
EEPROM and do not send ACK.
1001
Issue a START sequence.
Others
No operation, set the ERROR bit.
The EEPROM interface can also be operated by controlling the DIO4 and DIO5 pins directly. In
this case, a resistor has to be used in series with SDA to avoid data collisions due to limits in the
speed at which the SDA pin can be switched from output to input. Controlling DIO4 and DIO5 di-
rectly is discouraged, because it may tie up the MPU to the point where it may become too busy to pro-
cess interrupts.
Three-Wire (µ-Wire) EEPROM Interface
A 500 kHz three-wire interface, using SDATA, SCK and a DIO pin for CS is available. The interface is
selected by setting DIO_EEX = 2 (b10). The EECTRL bits when the three-wire interface is selected are
shown in Table 44. When EECTRL is written, up to 8 bits from EEDATA are either written to the EEPROM
or read from the EEPROM, depending on the values of the EECTRL bits.
The µ-Wire EEPROM interface is only functional when MPU_DIV[2:0] = 000.
Table 44: EECTRL Bits for the 3-Wire Interface
Control
Bit
Read/
Write
Name
Description
7
WFR
W
Wait for Ready. If this bit is set, the trailing edge of BUSY will be de-
layed until a rising edge is seen on the data line. This bit can be used
during the last byte of a Write command to cause the INT5 interrupt to
occur when the EEPROM has finished its internal write sequence. This
bit is ignored if HiZ = 0.
6
5
BUSY
HiZ
R
Asserted while the serial data bus is busy. When the BUSY bit falls, an
INT5 interrupt occurs.
W
Indicates that the SD signal is to be floated to high impedance immedi-
ately after the last SCK rising edge.
4
RD
W
W
Indicates that EEDATA is to be filled with data from EEPROM.
3:0
CNT[3:0]
Specifies the number of clocks to be issued. Allowed values are 0
through 8. If RD=1, CNT bits of data will be read MSB first and right
justified into the low order bits of EEDATA. If RD=0, CNT bits will be
sent MSB first to the EEPROM, shifted out of the MSB of EEDATA. If
CNT[3:0] is zero, SDATA will simply obey the HiZ bit.
The timing diagrams in Figure 11 through Figure 15 describe the 3-wire EEPROM interface behavior. All
commands begin when the EECTRL register is written. Transactions start by first raising the DIO pin that
is connected to CS. Multiple 8-bit or less commands such as those shown in Figure 11 through Figure 15
are then sent via EECTRL and EEDATA.
48
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