CT2565 datasheet(4/31 Pages) AEROFLEX

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SCDCT2565 REV B 8/10/99 Plainview NY (516) 694-6700

DMA- Type Handshake

All BC and RT word transfers are preceded by a

request-grant-acknowledge

format

DMA

handshake procedure.

Timing information is

provided in BC, RTU and MT sections.

In MT mode, the 1553 transmission is transferred

along with an identification Word using a single

DMA handshake containing two memory-write

operations.

The DMA format requires that the

subsystem provide a bus grant (BUSGRNT pin

45) low within a timeout period.

Note that

BUSGRNT should be set to logic "1" before

another bus request (BUSREQ) is issued.

Memory Read/Write

With the single exception of an RT command

word transfer, all subsystem transfers take the

form of a static memory read or write.

A low

pulse on both the chip select (CS) and output

enable (OE) or a low pulse on CS and write

enable (WE) (pins 17, 18 and 44 respectively)

indicates data is valid on the parallel data bus for

the duration of the pulse. The rising edge of CS

triggers an address increment (ADRINC pin) low

output pulse used to increment the subsystem

memory address for successive transfers.

BC OPERATION

In the BC mode, the CT2565 initiates all

MIL-STD-1553

data

and

control

message

transfers.

Figure 3 details specific message

transfer flow and Table 3 lists subsystem memory

allocation.

The subsystem, or host processor,

must provide a CT2565 protocol Control Word

(See Figure 4) and MIL-STD-1553 command and

data words. The CT2565 will transfer the RTU

status response and provide message transfer

validation during an active transfer.

All parallel

word transfers occur in the form of a DMA

(request-grant-acknowledge)

handshake

with

memory read or operation as shown in Figures 5

and 6.

Command Transfer

In the BC mode pulse BCSTART (pin 41) low.

Following the pulse, the CT2565 will initiate a

DMA handshake and memory read for; the

control, word, command word(s) and up to 32

data words. No handshake timeout is enforced in

the BC mode (CT2565) remains idle during

BUSREQ to BUSGRNT), however 1553 protocol

must be maintained.

Note that commands are named from the BC's

point-of-view

(for

example,

TRANSMIT

CMD

indicates the addressed RTU must transmit data).

BIT TIMES

COMMAND WD

SYNC

REMOTE TERMINAL

T/R

SUBADDRESS

DATA WORD

ADDRESS

MODE

COUNT/MODE CODE

DATA WORD

SYNC

DATA

STATUS WORD

SYNC

REMOTE TERMINAL

RESERVED

ADDRESS

PARITY

TERMINAL FLAG

DYNAMIC BUS

CONTROL

ACCEPTANCE

MESSAGE ERROR

INSTRUMENTATION

SUBSYSTEM FLAG

SERVICE REQUEST

BUSY

Note: T/R – Transmit/Receive, P – Parity

BROADCAST

COMMAND RCVD

Figure 2 – MIL-STD-1553 Word Types

MODE

RT/BC

(PIN 1)

(PIN 2)

Table 2 – Operating Modes

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