MAXQ3180 Maxim, MAXQ3180 Datasheet - Page 24

• Manufacturer Part Number: MAXQ3180
• Description: The MAXQ3180 is a dedicated electricity measurement front-end that collects and calculates polyphase voltage, current, power, energy, and many other metering and power-quality parameters of a polyphase load
• Manufacturer: Maxim

Low-Power, Multifunction, Polyphase AFE
more bytes than are required by the current command,
the extra bytes are either ignored (if the MAXQ3180 is
busy processing the previous command) or are inter-
preted as the beginning of a new command. If the mas-
ter sends fewer bytes than are required by the current
command, the MAXQ3180 waits for SPI timeout, then
drops the transaction and resets the communication
channel. The duration of the timeout can be configured
through the COM_TIMO register.
Figures 5 and 6 show typical 2-byte reading and writing
transfers (without CRC byte).
Individual message bytes sent through the SPI are
processed in a software routine contained in the ROM
firmware. For this reason, it is necessary to provide a
delay between successive bytes. This byte spacing
must be no less than 400 system clocks to ensure that
the MAXQ3180 has a chance to read and process the
byte before the arrival of the next one.
Figure 5. Read SPI Transfer
Figure 6. Write SPI Transfer
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SCLK
MOSI
MISO
SCLK
MOSI
MISO
SSEL
SSEL
00 01
10 01
0xC1
0xC1
Host Software Design
ADDRESS
ADDRESS
0xC2
0xC2
WRITING DATA TO MAXQ3180 THROUGH SPI INTERFACE
READING DATA FROM MAXQ3180 THROUGH SPI INTERFACE
NACK (0x4E)
ACK (0x41)
DATA LSB
DUMMY
To read any virtual power registers, the host must first
confirm that the DSPRDY bit of the IRQ_FLAG register
is set, which indicates the last DSP cycle has complet-
ed, then proceed to reading all the desired virtual
power registers. For best communication efficiency, it is
recommended to complete reading the virtual power
registers before reading other registers. Virtual power
register reads must be completed within 50% of DSP
cycle time, from the moment the DSPRDY bit is set. Do
not forget to clear the DSPRDY bit, otherwise, host soft-
ware is not able to detect the completion of the new
DSP cycle. The MAXQ3180 does not clear the bit; it
only sets the bit whenever a DSP cycle processing is
completed. Users can clear the bit directly after the
confirmation that the bit is set. Clearing the DSPRDY bit
does not affect the DSP processing. It is strongly rec-
ommended that CRC be enabled for both read and
write to achieve reliable communications.
ACK (0x41)
DATA MSB
ACK (0x41)
DUMMY
NACK (0x4E)
DATA LSB
DUMMY
DUMMY
ACK (0x41)
DATA MSB
DUMMY
DUMMY