Cray CRAY-1 - Page 177

I
SH/SI synchronous channel (disk channel) - The parcel in which the
error occurs causes a parity fault flag to set. When parcel 3
arrives. or if parcel 3 is in error, a memory reference is initi-
ated and the parity fault flag causes the channel error flag to
set which in turn generates an I/O interrupt request. The channel
error flag also deactivates the channel. Data parcels received
after the parcel in error are not sampled. Parcels received up to
and including the parcel in error are stored in memory. Any un-
sampled lower-order parcels are stored as zeros. Once the channel
is deactivated, no more resume pulses are sent to the DCU to request
the remainder of the data block.
AllQthg~ __ ~hannels - The channel samples and stores the data until
the parcel containing the error is received. At this time, the
channel
error flag is set and the data transfer proceeds as if no
error had occurred. The transfer continues until the disconnect
occurs or
until (CA) = (Cl) for a DV module channel. The inter-
rupt is then generated and the channel is deactivated.
2. Unexpected ready pulse
DU Module
DV/DK asynchronous channel - Data is held and the resume occurs
when the channel is reactivated. No error interrupt is generated.
SH/SI synchronous channel (disk channel) - The data is resumed
and thrown away. An error interrupt is generated. This channel
uses
this method to flag fire code errors.
All other channels - The data is resumed and thrown away. An
error interrupt is generated.
The input channel control logic for the DU module differs from the OJ module
in two respects.
1. When a parity error is detected, the condition is noted and saved
but the
Channel Error Flag (CE) is not set until the Input Dis-
connect pulse
arrives. This change prevents an error interrupt
request from occurring and no data is lost. The only interrupt
request that occurs in this situation is the normal one at dis-
connect time, even though the Channel Error Flag is set at this
time to indicate the parity fault condition.
2.
For the DU module, the input channel is not forced active by the
clear I/O signal. If, however, the channel is already active,
it remains active.
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