71M6543F/H and 71M6543G/GH Data Sheet
2.5.11.2 Three-Wire (µ-Wire) EEPROM Interface with Single Data Pin
A 500 kHz three-wire interface, using SDATA, SDCK, and a DIO pin for CS is available. The interface is
selected by setting DIO_EEX[1:0] = 10. The EECTRL bits when the three-wire interface is selected are
shown in Table 56. 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.
2.5.11.3 Three-Wire (µ-Wire/SPI) EEPROM Interface with Separate Di/DO Pins
If DIO_EEX[1:0] = 11, the 71M6543 three-wire interface is the same as above, except DI and DO are
separate pins. In this case, SEGDIO3 becomes DO and SEGDIO8 becomes DI. The timing diagrams
are the same as for DIO_EEX[1:0] = 10 except that all output data appears on DO and all input data is
expected on DI. In this mode, DI is ignored while data is being received on DO. This mode is compatible
with SPI modes 0,0 and 1,1 where data is shifted out on the falling edge of the clock and is strobed in on
the rising edge of the clock.
Table 56: EECTRL Bits for the 3-wire Interface
Control
Bit
Read/
Write
Name
WFR
Description
Wait for Ready. If this bit is set, the trailing edge of BUSY is delayed 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.
7
W
Asserted while the serial data bus is busy. When the BUSY bit falls, an
INT5 interrupt occurs.
BUSY
6
R
Indicates that the SD signal is to be floated to high impedance immediately
after the last SDCK rising edge.
Indicates that EEDATA (SFR 0x9E) is to be filled with data from EEPROM.
HiZ
RD
5
4
W
W
Specifies the number of clocks to be issued. Allowed values are 0
through 8. If RD = 1, CNT bits of data are read MSB first, and right
justified into the low order bits of EEDATA. If RD = 0, CNT bits are sent
MSB first to the EEPROM, shifted out of the MSB of EEDATA. If
CNT[3:0] is zero, SDATA simply obeys the HiZ bit.
CNT[3:0]
3:0
W
The timing diagrams in Figure 18 through Figure 22 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 18 through Figure 22
are then sent via EECTRL and EEDATA.
When the transaction is finished, CS must be lowered. At the end of a Read transaction, the EEPROM
drives SDATA, but transitions to HiZ (high impedance) when CS falls. The firmware should then
immediately issue a write command with CNT=0 and HiZ=0 to take control of SDATA and force it to a
low-Z state.
EECTRL Byte Written
INT5
CNT Cycles (6 shown)
Write -- No HiZ
SCLK (output)
D7
D6
D5
D4
D3
D2
SDATA (output)
SDATA output Z
BUSY (bit)
(LoZ)
Figure 18: 3-wire Interface. Write Command, HiZ=0.
v1.2
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