ACT3492 Просмотр технического описания (PDF) - Aeroflex Corporation

Номер в каталоге

Компоненты Описание

производитель

ACT3492

MIL-STD-1553B Remote Terminal, BUS Controller, or Passive Monitor Hybrid with Status Word Control Dual Low Power Monolithic BUS Tranceivers

Aeroflex Corporation 

All other Mode Commands are serviced internally by the RT. The Terminal Flag and Message Error Status

Bits and BIT Word contents are controlled by the RT; however the subsystem has the option to set the

Message Error Bit and to control the reset conditions for the Terminal Flag and Subsystem Flag Bits in the

Status Word, and the Transmitter Timeout, Subsystem Handshake, and Loop Test Fail Bits in the BIT

Word.

Synchronize Mode Commands

Once the RT has validated the command word and checked for the correct address, the SYNC line is set

low. The signal WC4 will be set low for a Synchronize mode command, and high for a Synchronize with

data word mode command (See Figure 9). In a Synchronize with data word mode command, SYNC

remains low during the time that the data word is received. Once the data word has been validated, it is

passed to the subsystem on the internal highway IH08-IH715 in two bytes using IUSTB as a strobe signal

and H/L as the byte indicator (high byte first followed by low byte). SYNC being low should be used on the

enable to allow IUSTB to clock synchronize mode data to the subsystem.

If the subsystem does not need to implement either of these mode commands, the SYNC signal can be

ignored, since the RT requires no response from the subsystem.

Transmit Vector Word Mode Command

Figures 8 and 17 illustrates the relevant signal timings for an RT receiving a valid Transmit Vector Word

mode command. The RT requests data by setting VECTEN low. The subsystem should use H/L to enable

first the high byte and then the low byte of the Vector word onto the internal highway IH08-IH715.

It should be noted that the RT expects the Vector word contents to be already prepared in a latch ready for

enabling onto the internal highway when VECTEN goes low. If the subsystem has not been designed to

handle the Vector word mode command, it will be the fault of the Bus Controller if the RT receives such a

command. Since the subsystem is not required to acknowledge the mode command, the RT will not be

affected in any way by Vector word circuitry not being implemented in the subsystem. It will however

transmit a data word as the Vector word, but this word will have no meaning.

Reset Mode Command

Figure 7 shows the relevant signal timings for an RT receiving a valid reset mode command. Once the

command word has been fully validated and serviced, the RESET signal is pulsed low. This signal may be

used as a reset function for subsystem interface circuitry.

Dynamic Bus Allocation

This mode command is intended for use with a terminal which has the capability of configuring itself into a

bus controller on command from the bus. The line DBCREQ (See Figure 7) cannot go true unless the

DBCACC line was true at the time of the valid command, i.e. tied low. For terminals acting only as RTs, the

signal DBCACC should be tied high (inactive), and the signal DBCREQ should be ignored and left

unconnected.

Use of the Busy Status Bit

The Busy Bit is used by the subsystem to indicate that it is not ready to handle data transfers either to or

from the RT.

The RT sets the bit to logic one if the BUSY line from the subsystem is active low at the time of the second

falling edge of INCLK after INCMD goes low. This is shown in Figures 14 and 20. Once the Busy bit is set,

the RT will stop all receive and transmit data word transfers to and from the subsystem. The data transfers

in the Synchronize with data word and Transmit Vector word mode commands are not affected by the Busy

bit and will take place even if it has been set.

It should be noted that a minimum of 0.5 µs subaddress decoding time is given to the subsystem before

setting of status bits. This allows the subsystem to selectively set the Busy bit if for instance one

Aeroflex Circuit Technology

7

SCD3492 REV B 6/26/01 Plainview NY (516) 694-6700

Share Link: