Repair manual

2-77
THEORY OF OPERATION
Table 2-15. SCSI Interface I/O Signal Lines
Pin # Name Mnemonic Function
26 - 34 Data DB0-DB7, Upon command, the data asserted by the
DBP host computer is transmitted via these I/O
Data signal lines to the SCSI bus. The
internal CPU on the SCSI transfers the data
on the SCSI bus to the Digital Palette for
processing.
41 Attention ATN This control line transmits the ATN signal
from the SCSI Board to the host computer.
It tells the host computer that the SCSI
Board has a message ready. Message
operation transfers information about
command conditions between the SCSI
Board and the host computer.
THE ATN CONDITION IS NOT
SUPPORTED AT THIS TIME.
43 Busy BSY This control line transmits the BSY signal
from the SCSI Board to the host computer
to indicate that the SCSI data bus is busy
(data being transmitted from SCSI bus to
Digital Palette).
Once the SCSI Board clears the BSY signal
(SCSI bus free), data can again be asserted
on the I/O data signal lines and transmitted
via the SCSI bus to the Digital Palette.
44 Acknowledge ACK This control line transmits the ACK signal
from the SCSI Board to the host computer.
It acknowledges that its request for data was
received.