CT2555 datasheet(19/36 Pages) AEROFLEX

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SCDCT2553 REV B 8/6/99 Plainview NY (516) 694-6700

MT OPERATION

Initiate a Reset in order to initialize the CT2553.

Configure the CT2553 as a Bus Monitor (MT) by

setting the appropriate Configuration Register

Bits. See Figure 24 for MT initialization Steps.

MEMORY

CONFIGURATION.

The

user

configures the memory by writing the start

address for 1553 data storage into the Stack

Pointer

location.

The

Monitor

Stack

will

automatically wrap around once the RAM has

been filled (i.e., location FFF(H) is followed by

location 0000). An example of a typical MT

Memory Map 4 given in Table 5.

START

SEQUENCE.

After

setting

the

CONTROLLER START bit in the Start/Reset

1. Reads the start address for 1553 data storage

from the Stack Pointer location. The Stack

Pointer location(s) will be overwritten with 1553

data once the MT mode has begun and 1553

data is written into locations 0100(H) and

0101(H)].

2. Stores the received 1553 word into memory.

3. Increments the Stack Pointer by 1.

4. Generates an Identification Word and stores

this value into memory.

5.Repeats steps 2-4 until a Reset condition

occurs.

MT IDENTIFICATION WORD. The Identification

word provides the CPU with information pertaining

to the received 1553 word. Its format is shown in

Figure 25, This information allows the user to

analyze the 1553 data.

THIS-RT: Each command appearing on either

1553

Bus

decoded

and

tested

for

Manchester/protocol

errors.

the

CT2553

receives a valid command word containing a

Command Sync and a RTU address equivalent to

the RTAD0-RTAD4 inputs (pins 10, 9, 50, 49, and

11, respectively), THIS-RT (pin 55) will be pulsed

low. This signal can be used to identify specific

1553 commands or for switching to RTU mode

upon receipt of a command to this address.

Table 5 – Typical MT Memory Map

HEX ADDRESS

FUNCTION

0000

First Received 1553 Word

0001

First Identification Word

0002

Second Received 1553 Word

0003

Second Identification Word

0004

•

0005

•

0006

•

0100

Stack Pointer (Fixed location)

•

FFFF

•

MSB

LSB

8 7 6 5 4 3 2 1 0

GAP TIME

WORD FLAG

THIS RT

BROADCAST

ERROR

COMMAND SYNC

1553 CHANNEL A/B

CONTIGUOUS DATA

MODE CODE

BIT NAME

DEFINITION

GAP TIME

Indicates the time between receipt of the

previous and current words.Time is

indicated in 0.5µs increments for a

maximum of 128 µs and goes to FF over

128µs. (See Word Gap bit.)

WORD FLAG

Always logic 1.

THIS RT

Logic 0 indicates RT address field of the

associated command or Status Word

matches the RT address field of the

CT2553.

BROADCAST

Logic 0 indicates the RTU address field of

the command or Status Word

corresponds to address 31 (decimal).

ERROR

Logic 1 indicates Manchester, Parity,

Sync and/or low bit counter.

COMMAND SYNC

Logic 1 indicates 1553 Command or

Status Word sync field. (Logic 0 indicates

a Data Word sync field in received word.)

1553 CHANNEL

A/B

Indicates word received on 1553 Bus A

(1) or Bus B (0).

CONTIGUOUS

DATA

Logic 1 indicates the word was received

within 2µs of the previous word. If logic 0,

bits 8-15 contain the measured gap

between the words.

MODE CODE

When logic 1, the data transferred is a

mode code command.

Figure 25 – MT Identification Word

START

ISSUE RESET COMMAND

CLEAR RAM

ISSUE START COMMAND

INITIALIZE STACK POINTER

SET CONFIGURATION

Figure 24 – MT Initialization

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