UT1553 데이터 시트보기 (PDF) - Aeroflex UTMC

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UT1553

Remote Terminal Multi-Protocol

Aeroflex UTMC 

3.6.2 Last 1553 Command Register (LCM)

The RTMP stores the last valid 1553 command word it

received in the LCM. The only exception is if the RTMP is

in the 1553B mode and it receives a Transmit Last

Command Word mode code. Figure 10 shows the

configuration of the LCM. (0410H after Master Reset.)

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

T T T T T T S S S S S WWW W W

A A AA A / AA A A A C C C C C

4 3 21 0R 43 21 0 43 2 1 0

MSB

LSB

3.7 Write Only Register

The RTMP has one register that is write only. This register

is the Stop Self-Test Register (SST). The host can terminate

the RTMP’s self-test execution by writing to the SST. When

the host performs a write to the SST, the RTMP terminates

all memory activity. The Self-Test Enable (STEN) bit in the

CTL is also reset, and the Self-Test Active (STACT) bit in

the OPS is reset. When writing to the SST, the 16-bit data

word is a Don’t Care.

4.0 REMOTE TERMINAL INTERFACE

OPERATION

The RTMP’s remote terminal interface is based on a shared

memory concept where the shared memory is the link

between the MIL-STD-1553 data bus and the host

subsystem (figure 11). All 1553 data, whether transmitted

or received, must at one time be stored in this defined

memory area. The RTMP accesses the shared memory area

with a conventional Direct Memory Access (DMA)

interface.

Since the RTMP can access data anywhere within the 64K

memory space, the host has to specify exactly where in

memory the data associated with each valid transmit or

receive command word or mode code is located. The host

specifies the 1553 data area locations by programming the

RTMP’s Base Pointer Data Register (BPD) and by

initializing the 64-word Pointer Block. The BPD tells the

RTMP where in memory the Pointer Block is located. The

Pointer Block in turn specifies the location in memory where

the data associated with each valid command word or mode

code resides.

Therefore, to control the RTMP’s operation, the host first

programs the BPD to provide the RTMP with three essential

pieces of information: (1) the location in memory of the 64-

word Pointer Block; (2) the type of data buffer -- single or

separate; and (3) the receive data buffer size. The host can

update the Base Pointer Data Register if a new 64-word

Pointer Block needs to be selected, but do not update the

BPD while the RTMP is processing a message transaction.

Figure 8 shows the BPD.

4.1 Programming the BPD

The host programs the ten most significant bits of the BPD

(BPA15 - BPA6) to point to the starting address of the 64-

word Pointer Block within the RTMP’s 64K address space.

The RTMP generates the least significant six address lines

to determine which of the words within the 64-word Pointer

Block to use for a specific 1553 transmission. The RTMP

does this by detecting the T/R bit and the subaddress bits of

the last 1553 command word (figure 12). Usually the six

least significant address lines, BPA5-BPA0, are part of the

T/ R bit and subaddress or mode code bits of the last

command word, respectively. In some cases, BPA5-BPA0

are forced to specific values: (1) when the RTMP stores the

command word on the data buffer; (2) when the single buffer

mode of operation is chosen; and (3) when a mode code is

received.

The Data Buffer Mode bit, BUFSL, is the next bit in the

BPD that the host programs. The state of BUFSL determines

whether the RTMP stores the 1553 receive data in a single

data buffer (BUFSL = 1) or in separate data buffers (BUFSL

= 0).

Finally, the host programs bits BSIZ3-BSIZ0 in the BPD to

tell the RTMP how large to make the separate data buffers.

A formula determines the size of the data buffer(s): take the

decimal equivalent of the binary number represented by

BSIZ3-BSIZ0, where BSIZ3 is the MSB. This number,

represented by X, can range in size from three to fifteen.

The actual size of the data buffers is equal to 2 X . This means

the data buffers can range from 8 to 32K words in length.

In the single buffer mode, bits BSIZ3-BSIZ0 determine the

size of this single buffer. In the separate buffer mode, all

data buffers are the same size. This means the system

designer must program the buffer size so thelargest possible

message the RTMP can receive over the 1553 bus fits within

the programmed buffer size.

4.2 RTMP Pointer Block

The RTMP’s Pointer Block is a contiguous block of 64, 16-

bit words. The RTMP uses this block of data as the actual

address pointer locations for the memory accesses

associated with each 1553 message transaction. Therefore,

the Pointer Block is divided into receive data pointers, of

which one location is for the single buffer mode, transmit

data pointers, a mode code command pointer location, and

a location for the current 1553 command word (figure 13).

The host must initialize the Pointer Block before enabling

the RTMP’s 1553 receivers

RTMP-17

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