User guide
Redpine Signals, Inc. Proprietary and Confidential. Page 98
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Figure 17: 32-bit mode
4.3 Slave Response
The SPI slave gives responses to the SPI Master‟s requests. These are as
follows:
A success/failure response at the end of receiving the command.
Refer Interactions in the physical interface (this structure is similar
for all following read/write operations) . This response is driven
with 8-bit mode during the Command and Address phase
and is then switched to 8-bit or 32-bit mode during the Data
phase as per the command issued.
o Success: 0x58 or0x00000058
o Failure: 0x52 or 0x00000052
An 8-bit or 32-bit start token is transmitted once the four
commands indicating a read request are received and the slave is
ready to transmit data. The start token is immediately followed by
the read-data.
o Start Token: 0x55 or 0x00000055
An 8-bit or 32-bit busy response in case a new transaction is
initiated while the previous transaction is still pending from the
slave side.
o Busy Response: 0x54 or 0x00000054
Bit ordering of slave response
The bit ordering is same as explained in Bit ordering of SPI transmission/reception.
For example, 0x58 response for 8-bit success is sent as
0 -> 1 -> 0 -> 1-> 1 -> 0 -> 0 -> 0 . That is 0 is sent first, then 1, then 0, then 1,
and so on.
4.4 Initialization
The Initialization Command is given to the Slave to initialize the SPI interface.
The SPI interface remains non-functional to any command before initialization
and responds only after successful initialization. Initialization should be done
only once after the power-on. The SPI Slave treats any subsequent initialization
commands before the reset as errors.
W0
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sclk
cs
data
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