Seagate Ultra 320 - Manual (Page 47)

Parallel SCSI Interface Product Manual, Rev. A ) 33
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.
2.5.59 Transmit 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.
2.5.60 Transmit REQ(ACK) period tolerance
The maximum tolerance that a SCSI device may subtract from the REQ(ACK) period.
2.5.61 Transmit 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.
2.5.62 Transmit 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.
2.5.63 Transmitter 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.
2.5.64 Transmitter 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.
2.6 Measurement 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.
2.6.1 SE 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.
2.6.2 SE Fast-20 measurement points