Seagate Ultra 160, Ultra 320 manual 3.2 P1 data valid/invalid state transitions

The SCSI initiator port shall begin the section A of its training pattern independent of the start of the SCSI tar- get ports training pattern if it detects the SEL and MSG true, and C/D and I/O false on the first assertion of the REQ signal. The SCSI initiator port shall transmit the following pattern:

For fast-320 the SCSI initiator port shall transmit the training pattern described by section A, section B, and section C in this subclause except that the polarity of DB(0, 1, 4, 5, 9, 10, 13, and 14) shall be inverted during transmission of section A, section B, and section C (i.e., where it is specified that these signals shall be asserted, they shall be negated, and where it is specified that these signals shall be negated, they shall be asserted). These signals shall return to their normal polarity after completion of training pattern

transmission.

Start of section A:

1.if precompensation is enabled, set the drivers to the strong driver state;

2.simultaneously assert ACK, P1, and DB(15-0) signals within the equivalent of 32 transfer periods of the first REQ assertion (e.g., 200 ns at Fast-160);

3.wait the equivalent of 32 transfer periods (e.g., 200 ns at Fast-160);

4.simultaneously negate ACK, P1, and DB(15-0) signals;

5.wait the equivalent of 32 transfer periods;

6.set precompensation to negotiated state;

7.simultaneously assert and negate ACK, P1, and DB(15-0) signals at the negotiated transfer period 64 times (e.g., (2 x 6.25) x 64 = 800 ns at Fast-160);

Start of section B:

1.wait the equivalent of 192 transfer periods from the first assertion of ACK in step 2 of section A (e.g., 1200 ns at Fast-160);

2.keep the P1, and DB(15-0) signals negated while continuing to assert and negate ACK at the negoti- ated transfer period for the equivalent of 8 transfer periods (e.g., 50 ns at Fast-160);

3.keep the P1, DB(15-0), and ACK signals negated for the equivalent of 8 additional transfer periods;

4.simultaneously assert and negate PA and DB(15-0) signals at twice the negotiated transfer period (i.e., simultaneously repeat a 1100b bit pattern 12 times on each signal) while asserting and negating ACK at the negotiated transfer period 24 times (e.g., (2 x 6.25) x 24 = 300 ns at Fast-160);

Start of section C:

1.assert and negate ACK at the negotiated transfer period 64 times and at the same time assert and negate P1 at twice the negotiated transfer period while repeating a 0000010011111011b bit pattern eight times on each of the DB(15-0) signals (e.g., 2 x 6.25 ns) x 64 = 800 ns at Fast-160).

At the completion of its training pattern, the SCSI initiator port continues asserting and negating the ACK signal at the negotiated transfer period (e.g., 6.25 ns transfer period at Fast-160) and the P1 signal at twice the nego- tiated transfer period (e.g., 12.5 ns transfer period at Fast-160). When the SCSI initiator port is ready to trans- fer data and the REQ/ACK offset value is not zero it shall reverse the phase of P1 (see Section 3.5.3.2 below).

3.5.3.2P1 data valid/invalid state transitions

The transmitting SCSI device port shall indicate the start of a data valid state by reversing the phase of the P1 signal coincident with a REQ or ACK assertion. This is accomplished by withholding the next transition of P1 at the start of the first two transfer periods of valid data. Beginning with the third valid data word, P1 shall be tog- gled every two transfer periods, coincident with a REQ or ACK assertion. The minimum duration of the data valid state is two transfer periods, and the data valid state shall consist of an even number of transfer periods.

Anytime the sending SCSI device port pauses the sending of data, it shall reverse the phase of P1 by withhold- ing the next transition of P1 at the start of the first two transfer periods that have invalid data. Beginning with the third transfer period with invalid data, P1 shall be toggled every two transfer periods until valid data is sent.

Parallel SCSI Interface Product Manual, Rev. A 71