Tandberg Data
Hardware Interface
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8-4
Tandberg SLR Reference Manual
8.3.2. Bus Signals
The control and data signals are listed below:
Signal Name
Description
BSY
(Busy)
An “or-tied” signal which indicates that the bus is oc-
cupied.
SEL
(Select)
An “or-tied” signal which is used by an Initiator to se-
lect a Target, or by a Target to reselect an Initiator.
C/D
(Control/Data)
A signal driven by the Target to signal whether control
or data information is on the bus. Assertion indicates
control.
I/O
(Input/Output)
A signal driven by the Target to control the direction of
the data bus with respect to the Initiator. Assertion in-
dicates input to the Initiator.
MSG
(Message)
A signal driven by the Target indicating the message
phase.
REQ
(Request)
A signal driven from the Target indicating a request for
an REQ/ACK handshake.
ACK
(Acknowledge)
A signal driven by an Initiator to indicate acknowledg-
ment of an REQ/ACK handshake.
ATN
(Attention)
A signal driven by an Initiator indicating that a mes-
sage is available for the Target.
RST
(Reset)
An “or-tied” signal which indicates the
Reset
condition.
DB(7-0)/DB(15-0) and
DB/DB(P1)
(Data Bus)
Eight or sixteen data bit signals comprise the data bus.
DB/ DB(15) are the most significant bits.
DB/DB(P1) are the data bus parity (odd).
Each of the data signals DB/DB(15) through DB is
uniquely assigned as a Target or Initiator bus address
(i.e. SCSI DEVICE ID). This identification is normally
assigned and strapped during system configuration.
Table 8.5 Summary of SCSI-bus Phases