SPI-3 technical change (part 2)

gop at us.ibm.com gop at us.ibm.com
Fri Nov 19 15:18:41 PST 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* gop at us.ibm.com
*
While reviewing Brea Technologies letter ballot comments with Bill Galloway
some issues came up that we agreed needed a wider audience before placing
the changes into SPI-3. In section 10.10 Signal restrictions between phases
 the I/O is not the only signal that causes a direction change. The C/D
line can cause the direction of the P_CRCA line to change. As a result (d)
below was added to the list. Any comments??
When the SCSI bus is between two information transfer phases, the following
restrictions shall apply to the SCSI bus signals:

a)The BSY, SEL, REQ, and ACK signals shall not change.

b)The C/D, I/O, MSG, and DATA BUS signals may change.

c)When switching the DATA BUS or P_CRCA signal direction from out
(initiator driving) to in (target driving), the target shall delay driving
the DATA BUS by at least a data release delay plus a bus settle delay after
asserting the I/O signal and the initiator shall release the DATA BUS no
later than a data release delay after the transition of the I/O signal to
true. When switching the DATA BUS direction from in (target driving) to out
(initiator driving), the target shall release the DATA BUS no later than a
system deskew delay after negating the I/O signal. The initiator shall
assert the DATA BUS no sooner than a system deskew delay after the
detection of the negation of the I/O signal.

d)The P_CRCA signal direction may switch direction while the DATA BUS does
not (e.g., changing from COMMAND phase to DT DATA OUT phase). When
switching the P_CRCA signal direction from out (initiator driving) to in
(target driving), the target shall delay driving the P_CRCA by at least a
data release delay plus a bus settle delay after negating the C/D signal
and the initiator shall release the P_CRCA signal no later than a data
release delay after the transition of the C/D signal to false. When
switching the P_CRCA signal direction from in (target driving) to out
(initiator driving), the target shall release the P_CRCA signal no later
than a system deskew delay after asserting the C/D signal. The initiator
shall negate the P_CRCA signal no sooner than a system deskew delay after
the detection of the assertion of the C/D signal.

e)The ATN and RST signals may change as defined under the descriptions for
the attention condition (see ) and hard reset (see ).

Bye for now,
George Penokie

Dept Z9V  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880


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