CT19901 datasheet(12/29 Pages) AEROFLEX

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SCDCT1990 REV B 8/21/00 Plainview NY (516) 694-6700

STATEN/

STATSTB

OUTPUT

Status Enable/Status Strobe - This line pulses low to enable the status word

onto the internal highway for transmission. When in RT mode this line must not

be used to enable data from the subsystem. This line also pulses high, when in

the Bus Control mode, to strobe received status words into the subsystem.

When PASMON is true this line pulses high for Command and Status words.

STAT UPDATE

INPUT

Status Update - When held low, causes TF or SSF to appear in Status Word

response to Transmit Status or Transmit Last Command issued immediately

after fault occurrence

BITEN/

RMDSTB

OUTPUT

Built In Test Enable/Receive Mode Data Strobe - This line pulses low when

servicing a valid and legal mode command to transmit the internal BIT word.

This signal is for information only and must not be used to enable data from the

subsystem. This line also pulses high when in the Bus Control mode when

mode data is received to be passed to the subsystem and when data is passed

to the subsystem during PASMON.

DWSYNC

OUTPUT

Data Word Sync - This line goes low if a data word sync and two Manchester

biphase bits are valid. CT1990 only.

ENABLE

INPUT

Enable - When held low, enables Bit Decode, Next Status, and Status Update

program lines.

CMSYNC

OUTPUT

Command Word Sync - This line goes low if a command word sync and two

Manchester biphase bits are valid. CT1990 only.

NDRQ

OUTPUT

No Data Required - This line goes low if the encoder transmit buffer is full i.e.

another word is going to be transmitted. This signal is for information only and

must not be used to enable data from the subsystem.

NEXT STAT

INPUT

Next Status - When held low, causes TF or SSF to appear in very next Status

Word after fault occurrence (except for Transmit Status or Transmit Last Com-

mand).

PASMON

INPUT

Passive Monitor - When functioning as a Bus Controller this line acts as a

passive monitor select. The active going edge of this line will cause the

REQBUS lines to be latched and that bus, now selected will be monitored so

long as PASMON remains low. All traffic on the bus will be handed, after

validation, to the subsystem via STATSTB for status and commands words,

and RMDSTB for data words.

BCOPSTB

INPUT

Bus Controller Operation Strobe - When functioning as a Bus Controller a

low going pulse on this line will initiate the selected bus controller operation on

the requested bus, using BCOPA&B and REQBUSA&B.

RMDSTB

See BITEN/RMDSTB.

BCOPA

INPUT

Bus Control Operation A - Least significant bit of the bus controller operation

select lines.

BCOPB

INPUT

Bus Control Operation B - Most significant bit of the bus controller operation

select lines.

REQBUS A

BI-DIRECTIONAL

Request Bus A - This line, when in RT mode, is the least significant bit of the

bus request lines which specify the origin of the command, i.e. they are

sources. When in BC mode these lines are sinks and specify which bus is to be

used for the next command.

REQBUS B

BI-DIRECTIONAL

Request Bus B - Most significant bit of the bus request lines. (See above for

description.)

Pin Description (Cont.)

Signal

Direction

Signal Description

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