Linear Technology LTC6804-1 - Page 47

LTC6804-1/LTC6804-2
47
680412fc
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operaTion
go high when CSB goes high even if the device has not
completed the conversion. See Programming Examples on
how to use the PLADC command with devices in parallel
configuration.
In parallel configurations that communicate in isoSPI
mode, the low side port transmits a data pulse only in
response to a master isoSPI pulse received by it. So,
after entering an address command in either method of
polling described above, isoSPI data pulses are sent to
the part to update the conversion status. These pulses
can be sent using LTC6820 by simply clocking its SCK
pin. In response to this pulse, the LTC6804-2 returns an
isoSPI pulse if it is still busy performing conversions and
does not return a pulse if it has completed conversions. If
a CSB high isoSPI pulse is sent to the LTC6804-2, it exits
the polling command. Note that broadcast poll commands
are not compatible with parallel isoSPI.
Bus Protocols
Protocol Format: The protocol formats for both broadcast
and address commands are depicted in Table 27 through
Table 31. Table 26 is the key for reading the protocol
diagrams.
Table 26. Protocol Key
CMD0 First Command Byte (See Tables 32 and 33)
CMD1 Second Command Byte (See Tables 32 and 33)
PEC0 First PEC Byte (See Table 25)
PEC1 Second PEC Byte (See Table 25)
n Number of Bytes
… Continuation of Protocol
Master to Slave
Slave to Master
Figure 23. SDO Polling After an ADC Conversion Command
Figure 24. SDO Polling Using PLADC Command
680412 F23
SDI
SCK
t
CYCLE
SDO
CSB
MSB(CMD) LSB(PEC)BIT 14(CMD)
680412 F24
SDI
SCK
SDO
CSB
MSB(CMD) LSB(PEC)
CONVERSION DONE
BIT 14(CMD)