RE: [t13] SATA question about HOLD & EOF

[John Masiewicz]

Dan, If the host has an EOF ready to transmit when a HOLD is received, it should send the EOF. The Link Transmit state diagram does not allow the sending of HOLDA between CRC and data Dwords.  The reasoning is that the host does not have to respond to the hold immediately, there is a 20 Dword latency requirement that gives the host the latitude to send the EOF and immediately WTRM. It is faster to complete the frame than to respond with the HOLDA. If the EOF has been transmitted, the HOLD is ignored following the specification (since there is no HOLD except between SOF & EOF, it is ignored). Also, it should be remembered that just because a Dword is on the bus, it is not necessarily “received” by the link, there is a delay. If you look in the Link receive state machine state LR4, arc 3, you will see R_IP is transmitted before the CRC, and then the transition and transmission of CRC word and EOF are mandatory transitions, as long as SYNC is not received. For the case of your host that sends HOLDA between CRC and EOF, it isn’t good bus behavior, and it might be argued that it is illegal, but you should not fail for it. Many SATA implementations automatically respond with HOLDA in HW as fast as possible. If you consider the latency, it is not unusual in my experience to have spurious HOLDs and unsent HOLDAs, depending on the situation. I do not think a recipient should fail for the HOLDA before EOF, and I would argue that the recipient is required to ignore the HOLD in that case, so there is no failure.   John Masiewicz Western Digital     From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dan Meyer Sent: Tuesday, September 20, 2005 1:06 PM To: forum@t13.org Subject: [t13] SATA question about HOLD & EOF               Pardon me if this is the incorrect forum for this question and please direct me to the correct forum if this is the case.               When a host has EOF to send and a device sends HOLD, should the host send EOF or HOLDA?  In Serial ATA rev 1.0a section 7.6.1.3 state LT8 (page 167), I see no mention of HOLD, only “When in this state, the Link layer shall transmit the EOF primitive.”  I am seeing a host who sends HOLDA instead of EOF.         Dan Meyer