SMP REQUEST/SMP RESPONSE timer query
apoorva.vats at synopsys.com
Wed Aug 21 23:53:45 PDT 2013
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As specified in "SAS Protocol Layer - 3 (SPL-3) " version specification
(T10/BSR INCITS 492)( Revision 02 / 16 January 2013)
Page no. 443
6.20 SMP link layer
6.20.1 SMP frame transmission and reception
Inside an SMP connection, the SMP initiator phy transmits a single
SMP_REQUEST frame within 100 ìs and the SMP target phy responds with a single
SMP_RESPONSE frame (see 8.4) within 1 900 ìs.
And at page no. 547
Table 187 - MT_TP time
SMP Response time limit
1 900 ìs
Maximum time from receiving an SMP_REQUEST frame to transmitting an
Here specification specifies 2 timers. 1 for Request frame and other for
1) 100 ìs timer runs at Initiator end and;
2) 1900 ìs timer runs at Target end.
And at page no.548
220.127.116.11.3 MT_TP2:Respond state
18.104.22.168.3.1 State description
This state waits for a Send SMP Response request, which includes the
a) Response Bytes.
After receiving a Send SMP Response request, this state shall construct an
SMP_RESPONSE frame using the arguments from the Send SMP Response request and
send a Transmit Frame request to the port layer within the SMP Response time
limit specified in table 187 (see 22.214.171.124.1).
This specifies that within SMP Response time limit SMP RESPONSE frame should
be sent by the Target but no action is specified in the specification, if
this does not happen within this time limit.
Similarly, Specification does not mention anything if SMP initiator phy does
not transmit SMP_REQUEST frame within 100 ìs.
Firstly, I have few queries regarding 100 us timer :-
1) What happens if Initiator doesn't transmit SMP REQUEST frame even after
100 ìs get passed after the connection is established?
2) Why this timer is running in SMP Initiator instead of SMP Target ? I
believe the SMP Target should wait for 100 us after SMP connection is
established to receive a SMP Request Frame.
Secondly, following queries are with respect to 1900 us time limit:
3) What happens if Target doesn't transmit SMP RESPONSE frame even after 1900
ìs get passed after receiving SMP REQUEST frame.
4) Why this timer is running in SMP Target instead of SMP Initiator ? I
believe the SMP Initiator should wait for 1900 us after SMP request is sent
to receive a SMP Response Frame.
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