SN75970B

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS323A – NOVEMBER 1999 – REVISED JANUARY 2000

3

POST OFFICE BOX 655303

Terminal Functions

TERMINAL

LOGIC

I/O

TERMINATION

DESCRIPTION

NAME

NO.

LEVEL

I/O

TERMINATION

DESCRIPTION

AACK –

8

TTL

I/O

strong pullup

SCSI acknowledge (– ACK) signal to/from controller

AATN –

6

TTL

I/O

strong pullup

SCSI attention (– ATN) signal to/from controller

ABSY –

25

TTL

I/O

strong pullup

SCSI busy (– BSY) signal to/from the controller

AC/D –

11

TTL

I/O

strong pullup

SCSI control/data (– C/D) signal to/from the controller

AI/O –

22

TTL

I/O

strong pullup

SCSI input/output (– I/O) signal to/from the controller

AMSG –

21

TTL

I/O

strong pullup

SCSI message (– MSG) signal to/from the controller

AREQ –

10

TTL

I/O

strong pullup

SCSI request (– REQ) signal to/from controller

ARST –

27

TTL

I/O

strong pullup

SCSI reset (– RST) signal to/from the controller

ASEL –

23

TTL

I/O

strong pullup

SCSI select (– SEL) signal to/from the controller

BACK –

51

RS-485

I/O

weak pullup

SCSI acknowledge (– ACK) signal to/from the bus

BACK+

50

RS-485

I/O

weak pulldown

SCSI acknowledge (+ACK) signal to/from the bus

BATN –

53

RS-485

I/O

weak pullup

SCSI attention (–

BATN+

52

RS-485

I/O

weak pulldown

SCSI attention (+ATN) signal to/from the bus

BBSY –

31

RS-485

I/O

weak pulldown

SCSI busy (– BSY) signal to/from the bus

BBSY+

32

RS-485

I/O

weak pullup

SCSI busy (+BSY) signal to/from the bus

BC/D –

47

RS-485

I/O

weak pullup

SCSI control/data (– C/D) signal to/from the bus

BC/D+

46

RS-485

I/O

weak pulldown

SCSI control/data (+C/D) signal to/from the bus

BI/O –

36

RS-485

I/O

weak pullup

SCSI input/output (– I/O) signal to/from the bus

BI/O+

35

RS-485

I/O

weak pulldown

SCSI input/output (+I/O) signal to/from the bus

BMSG –

38

RS-485

I/O

weak pullup

SCSI message (– MSG) signal to/from the bus

BMSG+

37

RS-485

I/O

weak pulldown

SCSI message (+MSG) signal to/from the bus

BREQ –

49

RS-485

I/O

weak pullup

SCSI request (– REQ) signal to/from the bus

BREQ+

48

RS-485

I/O

weak pulldown

SCSI request (+REQ) signal to/from the bus

BRST –

29

RS-485

I/O

weak pulldown

SCSI reset (– RST) signal to/from the bus

BRST+

30

RS-485

I/O

weak pullup

SCSI reset (+RST) signal to/from the bus

BSEL –

33

RS-485

I/O

weak pulldown

SCSI select (– SEL) signal to/from the bus

BSEL+

34

RS-485

I/O

weak pullup

SCSI select (+SEL) signal to/from the bus

CLK40

4

CMOS

I

strong pulldown

40-MHz clock input

DRVBUS

19

TTL

O

N/A

Driver bus. A high-level logic signal that indicates the SCSI bus is in one of

the information transfer phases.

DSENS

3

TTL

I

weak pullup

A low-level input initializes the internal latches and disables all drivers.

GND

5, 13–17,

40–44

N/A

N/A

N/A

Supply common

RESET

2

TTL

I

weak pullup

Reset. A low-level input initializes the internal latches and disables all drivers.

RSTFLTR

1

TTL

I

weak pullup

Reset filter. Filtered input from the SCSI bus for a system reset. RSTFLTR

differs from RESET by keeping the ARST and BRST drivers enabled.

SDB

20

TTL

O

N/A

A high-level logic signal that indicates a differential to single-ended data flow.

TEST

7

TTL

I

weak pulldown

Test. A high-level input that places the device in a test mode (see Table 1).

It is grounded during normal operation.

TIMEOUT

9

Analog

I/O

N/A

Time out. This signal connects to an external RC time constant for a time out

during bus arbitration.

VCC

12, 18, 39, 45

N/A

N/A

N/A

5-V supply voltage

X1 /CLK20

55

CMOS

I

none

20-MHz crystal oscillator or clock input

X2

56

Analog

O

none

20-MHz crystal oscillator feedback