UT1553B View Datasheet(PDF) - Aeroflex UTMC

Part Name

Description

Manufacturer

UT1553B

RTI Remote Terminal Interface

Aeroflex UTMC 

Last Command Register (Read Only)

The 16-bit read-only Last Command Register provides the host with last command and operational status information. The

RTI transmits the lower 11 bits of this register along with terminal address upon receipt of a Transmit Last Command mode

code. Read the Last Command Register by applying a logic zero to CS, CTRL, and a logic one to RD/WR and ADDR IN (0).

The 16-bit contents of the Last Command Register are read from data I/O pins DATA(15:0).

Bit

Number

Initial

Condition

Description

0 through 10

[all 1s]

Least significant 11 bits of the last command word.

11

[0]

Busy Bit. System Register bit 10.

12

[0]

Self-test. System Register bit 11.

13

[1]

Terminal Flag Enabled. System Register bit 9.

14

[1]

Channel A/B. System Register bit 6.

15

[1]

Illegal Command. The RTI illegalized the last command.

1.3 Mode Codes and Subaddresses

The UT1553B RTI provides subaddress and mode code

decoding meeting MIL-STD-1553B. In addition, the device

has automatic internal illegal command decoding for

reserved MIL-STD-1553B mode codes. Upon command

word validation and decode, status pins MCSA(4:0) and

MC/SA become valid. Status pin MC/SA will indicate

whether the data pins MCSA(4:0) are mode code or

subaddress information. Status Register bits 5 through 0

contain the same information as pins MCSA(4:0) and MC/

SA.

The system designer can use signals MCSA(4:0), MC/SA,

BRDCST, XMIT, and RCV to illegalize mode codes,

subaddresses, and other message formats via the Illegal

Command (ILL COMM) input (see figure 23 on

page 36).

The RTI will internally decode the following mode codes

as illegal:

- Dynamic Bus Control

- Selected Transmitter Shutdown

- Override Selected Transmitter Shutdown

- All Reserved Mode Codes

If the RTI receives one of the above mode codes, the RTI

responds by transmitting a status word with the Message

Error bit set to logic one.

Mode codes which involve data transfer are processed like

receive and transmit commands. The RTI will not generate

DMA request for Transmit Status Word and Transmit Last

Command mode codes since the information is stored

internal to the RTI.

The following mode codes require assistance from the host:

- Synchronize

- Initiate Self-Test

- Reset Remote Terminal

For example, the RTI will accept and respond to a Reset

Remote Terminal mode code; however it will not perform

a reset operation. The host must interpret the mode code and

take appropriate action.

The RTI does not define or interpret the following data

words associated with mode code commands:

- Transmit Vector Word

- Synchronize With Data Word

- Transmit Bit Word

The RTI will accept and respond to mode code with data;

the host must interpret or define the data word. The RTI will

store or retrieve the data required for mode code command

from block #1 of the receive or transmit page

.

RTI-7

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