Bus Signals - Fujitsu Scan Partner 300C Instruction Manual

4.2.2 Bus signals

Signal name
Data
Control Signals
Table 4-2
Type of signal
Eight data-bit signals, plus a parity-bit signal that forms a DATA
DB0
DB(7)
BUS.
DB1
priority during the ARBITRATION phase. Bit number,
DB2
significance and priority decease downward to DB(O). A data bit
DB3
is defined as one when the signal value is true. A data bit is
DB4
defined as zero when the signal value is false. Data parity DB(P)
DB5
shall be odd. Parity is undefined during the ARBITRATION
DB6 phase.
DB7
(Data Bus n)
DBP
(Data Bus Parity)
An "ORtied" signal that indicates that the bus is being used
BSY (Busy)
An "ORtied" signal used either by an initiator to select a target or
SEL (Select)
by a target to reselect an initiator
RST (reset) An "ORtied" signal that indicates the RESET condition
C/D (Control/Data) The C/D, I/O, and MSG signals are used to distinguish between
I/O (Input/Output) the different information transfer phases.
MSG Message
REQ (request) A signal driven by an initiator to indicate a request for a
REQ/ACK data transfer handshake
ACK (acknowledge) A signal driven by an initiator in indicate and acknowledgment
for REQ/ACK data transfer handshake.
ATN (Attention) A signal driven by an initiator to indicate the ATTENTION
condition
Bus signals
the
is most significant bit and has the highest
4-7
Initiator
⇐
⇒
Target
⇐
⇒
⇐
⇒
⇐
⇒
⇐
⇒
⇐
⇐
⇒
⇒