CT2565 Datasheet, PDF (14/31 Pages) Aeroflex Circuit Technology – CT2565 Bus Controller, Remote Terminal and BUS Monitor FOR MIL-STD-1553B

RTU Commands
A command word transfer will be initiated by the
CT2565 after the rising edge of NBGRNT (See
Figure 14). In order to allow the command word to be
stored in user-defined memory space (separate from
data), no memory write operation (CS, WR, ADRINC
outputs) will be initiated following the usual DMA-type
handshake; a Start Of Message (pin 78: SOM low)
pulse indicates that the CMD word is currently valid on
the data bus. Note that commands are named from
the BC point-of-view (i.e., a TRANSMIT CMD dictates
that the addressed RTU must transmit data).
Transmit CMD (RT-BC)
If the subsystem is available (pin 47: SSBUSY high):
following transmission of the status word, the CT2565
will initiate a handshake/memory-read respectively for
the total number of (data) words defined by the
Command Word-word count field. Figure 15 shows
the RTU Read/Write Timing. Note that possible data
word transfer and short-loop test errors will be
reflected in the following status word/bit word. A low
on the SSBUSY input will set the corresponding status
word flag, and no data transfer will be requested
(BUSREQ low) following transmission of the status
word.
Receive CMD (BC-RT). A DMA handshake will be
initiated for each word received over the 1553 data bus
(See Figure 16). If successful, the respective
handshake will be followed by a corresponding
memory write. Transfer errors such as handshake
timeout or SS BUSY will not terminate transfer
attempts for the remaining data words, error flagging
or status word transmission.
RTU(b)-RTU(a) (Transmit/Receive). An RT-RT
transfer will appear to both RTU subsystems as a
standard transmit or receive command except: (1)
transmission of the data block will not be continuous
with that of the receive CMD, and, (2) upon detection
of a command-sync field following the receive CMD,
RTU(a) will recognize an RT-RT transfer and store the
transmit CMD-address field for comparison with the
address field of the following (RTU(b) status) word
(See Figures 17 and 18). If a mismatch is detected,
RTU(a) will issue a message error. The transmitting
RTU will respond as in an RT-BC Transmit CMD.
RTU Status/Error Handling
Message transfer errors are indicated using the
TIMEOUT, HSFAIL, MSGERR and LOOPERR
RTU-status outputs (pins 4, 5, 30 and 46 respectively).
Additional error detection mechanisms available
include status input manipulation (below) and
evaluation of the status and BIT words (See BIT
Word).
Table 6 describes error handling mechanisms related
to each stage in a message transfer (reading left to
right) as well as noting errors associated with a
specific CT2565 status output (reading right to left).
Short Loop Test. The last word to be transmitted in a
given message transfer (Status word, BIT word or
Data word) is stored in a CT2565 internal register. As
this word is transmitted to the 1553 bus, it is "looped
back" through the active receiver channel for
auto-RTU, "SHORTLOOP" verification. A LOOPERR
low pulse indicates a mismatch between the stored
and looped words. Note that short loop testing is
initiated for all RTU transfers except a Broadcast
transfer.
TRANSFER/CONDITION
DESCRIPTION
ERROR SIGNAL PIN
COMMAND WORD
Invalid Word Format
Invalid Command (format error)
Handshake Failure
Illegal Mode Command
RT-RT Transfer
Response Timeout
Address mismatch
DATA WORD
Handshake Failure
Transmit Command
Receive Command
Number Transmitted ⁽²⁾
LOOP WORD
Short Loop
Long Loop
Sync, bit count invalid.
Operation disagreement (e.g. Broadcast and
Transmit bits set)
BUSREQ to BUSGRNT timeout
Subsystem set ILLCMD (pin 48).
(Transmit) Command to Status Word time.
Transmit Command Address ≠ Status Word
address.
BUSREQ to BUSGRNT timeout
(Continue)
(Message terminated)
Low data word-count received.
High data word count
Looped back through receiver.
Received word ≠ to last xmitted 1553 word.
(BC only)
None; input ignored
-
MSGERR (also; SW bit)
30
HSFAIL, suppress
5
SOM, continue
78
SW message error bit set
TIMEOUT (transmitting RT) 4
(also; MSGERR bit)
MSGERR (Receiving RT)
30
(also; MSGERR bit)
HSFAIL ⁽¹⁾
5
Continue message transfer
INCMD high, EOM
9,57
MSGERR ⁽³⁾ (SW bit)
30
MSGERR after validation
30
(no transfer) SW and BIT-
Word also set.
LOOPER (also sets Ter-
Flag bit).
46
Notes:
(1) The HSFAIL low output is reset (high) at the start of the next message transfer (NBGRNT low).
(2) The subsystem can use the status input pins (SW) to report incorrect word count type errors.
(3) MSGERR set 7.5µS after last mid parity bit of last data word.
Table 6 – RTU Error Handling
Aeroflex Circuit Technology
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