Seagate Ultra 160, Ultra 320 manual Measurement points

The minimum time that a SCSI target port shall negate the REQ signal while using synchronous transfers or paced transfers, provided it is not transitioning P_CRCA during data group transfers. Also, the minimum time that a SCSI initiator port shall negate the ACK signal while using synchronous transfers or paced transfers.

2.5.59Transmit setup time

For ST data transfers, the minimum time provided by the transmitting SCSI device between the changing of Data Bus, DB(P_CRCA), and/or DB(P1) and the assertion of the REQ signal or the ACK signal while using synchronous data transfers. For DT data transfers, the minimum time provided by the transmitting SCSI device between the changing of Data Bus, DB(P_CRCA), and/or DB(P1) and the transition of the REQ signal or the ACK signal.

2.5.60Transmit REQ(ACK) period tolerance

The maximum tolerance that a SCSI device may subtract from the REQ(ACK) period.

2.5.61Transmit REQ assertion period with P_CRCA transitioning

The minimum time that a SCSI target port shall assert the REQ signal while transitioning P_CRCA during data group transfers. Specified to provide the increased receive REQ assertion period, subject to loss on the inter- connect.

2.5.62Transmit REQ negation period with P_CRCA transitioning

The minimum time that a SCSI target port shall negate the REQ signal while transitioning P_CRCA during data group transfers. Specified to provide the increased receive REQ negation period, subject to loss on the inter- connect.

2.5.63Transmitter skew

The maximum difference in time allowed between the rising or falling edge of a “1010...” pattern on the DATA BUS or DB(P1) signal and its clocking signal on the ACK or REQ signal as measured at their zero-crossing points. The signals for the output waveforms shall be measured at the connector of the transmitting device.

2.5.64Transmitter time asymmetry

The maximum time on DATA BUS, DB(P1), ACK, or REQ signal from any transition edge to the subsequent transition edge during a “1010...” pattern, as measured at their zero-crossing points, minus the data transfer period. The signals for the output waveforms shall be measured at the connector of the transmitting device.

2.6Measurement points

The measurement points for low voltage differential (LVD) ACK, REQ, DATA, P_CRCA, and PARITY signals are defined in ANSI standard SPI-5 section 9.3. All measurements are at the SCSI connector.

When paced transfers are enabled, the timing shall be measured relative to the zero crossing of the differential signal. In paced transfers the timing budget and receiver masks account for the differences between the setup and hold detection thresholds that occur for synchronous transfers.

2.6.1SE Fast-5 and Fast-10 measurement points

SE SCSI devices with data transfer rates up to and including Fast-10 shall use the measurement points defined in Section 9 of ANSI standard SPI-4, for the measurement of the timing values. The rise and fall times for the SE REQ/ACK signals shall be nominally the same as for the SE Data, DB(P_CRCA), and DB(P1) sig- nals.

2.6.2SE Fast-20 measurement points

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