SN260 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'SN260' PDF : 88 Pages View PDF
SN260
6.2.7
SPI protocol
Error conditions
If two or more different error conditions occur back to back, only the first error condition will
be reported to the Host (if it is possible to report the error). The following are error conditions
that might occur with the SN260.
● Oversized EZSP frame
If the transaction includes an EZSP Frame, the Length Byte cannot be a value greater
than 125. If the SN260 detects a length byte greater than 125, it will drop the incoming
Command and abort the entire transaction. The SN260 will then assert nHOST_INT
after Slave Select returns to Idle to inform the Host through an error code in the
Response section what has happened. Not only is the Command in the problematic
transaction dropped by the SN260, but the next Command is also dropped, because it
is responded to with the Oversized EZSP Frame Error Response.
● Aborted transaction
An aborted transaction is any transaction where Slave Select returns to Idle
prematurely and the SPI Protocol dropped the transaction. The most common reason
for Slave Select returning to Idle prematurely is the Host unexpectedly resetting. If a
transaction is aborted, the SN260 will assert nHOST_INT to inform the Host through an
error code in the Response section what has happened. When a transaction is
aborted, not only does the Command in the problematic transaction get dropped by the
SN260, but the next Command also gets dropped since it is responded to with the
Aborted Transaction Error Response.
● Missing frame terminator
Every Command and Response must be terminated with the Frame Terminator byte.
The SN260 will drop any Command that is missing the Frame Terminator. The SN260
will then immediately provide the Missing Frame Terminator Error Response.
● Long transaction
A Long Transaction error occurs when the Host clocks too many bytes. As long as the
inter-command spacing requirement is met, this error condition should not cause a
problem, since the SN260 will send only 0xFF outside of the Response section as well
as ignore incoming bytes outside of the Command section.
● Unresponsive
Unresponsive can mean the SN260 is not powered, not fully booted yet, incorrectly
connected to the Host, or busy performing other tasks. The Host must wait the
maximum length of the Wait section before it can consider the SN260 unresponsive to
the Command section. This maximum length is 200 milliseconds, measured from the
end of the last byte sent in the Command Section. If the SN260 ever fails to respond
during the Wait section, it is valid for the Host to consider the SN260 unresponsive and
to reset the SN260. Additionally, if nHOST_INT does not assert within 10ms of nWAKE
asserting during the wake handshake, the Host can consider the SN260 unresponsive
and reset the SN260.
6.3
SPI protocol timing
Figure 6 illustrates all critical timing parameters in the SPI Protocol. These timing
parameters are a result of the SN260’s internal operation and both constrain Host behavior
and characterize SN260 operation. The parameters shown are discussed elsewhere in this
document. Note that Figure 6 is not drawn to scale, but is provided to illustrate where the
parameters are measured.
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