71m6521be Maxim Integrated Products, Inc., 71m6521be Datasheet - Page 42

• Manufacturer Part Number: 71m6521be
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

Status
A byte is read by writing the ‘Receive’ command (CMD = 0001) to EECTRL and waiting for the BUSY bit to fall. Upon comple-
tion, the received data is in EEDATA. The serial transmit and receive clock is 78kHz during each transmission, and the clock is
held in a high state until the next transmission. The bits in EECTRL are shown in Table 56.
Three-Wire EEPROM Interface
A 500kHz three-wire interface, using SDATA, SCK, and a DIO pin for CS is available. The interface is selected with
DIO_EEX=3. The same 2-wire EECTRL register is used, except the bits are reconfigured, as shown in Table 57. 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 timing diagrams in Figure 9 through Figure 13 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 9 through Figure 13 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 will be driving SDATA,
but will transition 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.
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3-0
Bit
7
6
5
4
The EEPROM interface can also be operated by controlling the DIO4 and DIO5 pins directly. However, controlling
DIO4 and DIO5 directly is discouraged, because it may tie up the MPU to the point where it may become too
busy to process interrupts.
CMD[3:0]
RX_ACK
TX_ACK
ERROR
Name
BUSY
Read/
Write
W
R
R
R
R
Reset
State
0000
0
0
1
1
© 2005-2008 TERIDIAN Semiconductor Corporation
see CMD
Negative
Negative
Polarity
Positive,
Positive
Positive
Table
Table 56: EECTRL Status Bits
Description
1 when an illegal command is received.
1 when serial data bus is busy.
0 indicates that the EEPROM sent an ACK bit.
0 indicates when an ACK bit has been sent to the EEPROM
Others
CMD
0000
0010
0011
0101
0110
1001
Operation
No-op. Applying the no-op command will stop the I
(SCK, DIO4). Failure to issue the no-op command will keep
the SCK signal toggling.
Receive a byte from EEPROM and send ACK.
Transmit a byte to EEPROM.
Issue a ‘STOP’ sequence.
Receive the last byte from EEPROM and do not send ACK.
Issue a ‘START’ sequence.
No Operation, set the ERROR bit.
Energy Meter IC
71M6521BE
DATA SHEET
JANUARY 2008
2
C clock
V1.0