Z53C80 datasheet(6/40 Pages) ZILOG

6 / 40 page

Z53C80 SCSI

PS97SCC0200

ZILOG

SCSI BUS

The following signals are all Bi-directional, active Low,

open-drain, with 48 mA sink capacity. All pins interface

directly with the SCSI Bus.

/ACK

/Acknowledge (Bi-directional, Open-Drain, Active

Low). /ACK is driven by the Initiator and indicates an

acknowledgment for a SCSI data transfer. /ACK is received

as a response to the /REQ Signal in the Target role.

/ATN

/Attention (Bi-directional, Open-Drain, Active Low).

/ATN is driven by the Initiator and indicates an attention

condition. /ATN is received and is responded to by entering

the Message Out Phase in the Target role.

/BSY

/Busy (Bi-directional, Open-Drain, Active Low). /BSY

indicates that the SCSI Bus is being occupied. /BSY can be

driven by both the Target and the Initiator device.

/C//D

/Control//Data (Bi-directional, Open-Drain, Active

Low). /C//D indicates Control or Data information is on the

SCSI Bus. This signal is driven by a Target and is received

by the Initiator.

/I//O

/Input//Output (Bi-directional, Open-Drain, Active Low).

/I//O is driven by a Target and controls the direction of data

transfer on the SCSI Bus. When asserted, this signal

indicates input to the Initiator. When not asserted, this

signal indicates output from the Initiator. This signal is also

used to recognize the difference between the Selection

and Reselection Phases.

/MSG

/Message (Bi-directional, Open-Drain, Active Low).

The Target drives /MSG active during the Message Phase

and is received by the Initiator.

/REQ

/Request (Bi-directional, Open-Drain, Active Low).

Received by the Initiator and driven by a Target, /REQ

indicates a request for an SCSI data-transfer handshake.

/RST

SCSI Bus RESET (Bi-directional, Open-Drain, Active

Low). The /RST signal shows a SCSI Bus RESET condition

has occurred.

/DB7-/DB0,/DBP

/Data Bits, /Parity Bits (Bi-directional,

Open-Drain, Active Low). These eight data bits (/DB7-/

DB0), plus a parity bit (/DBP) form the SCSI Data Bus. /DB7

has the highest priority during the Arbitration phase and is

the most significant bit (MSB). Data parity is odd and is

always generated and optionally checked, which is not

valid during Arbitration.

/SEL

/Select (Bi-directional, Open-Drain, Active Low).

/SEL is used by a Target to select an Initiator, or by an

Initiator to reselect a Target.

Z53C80 Datasheet(PDF) 6 Page - Zilog, Inc.

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