CT2553 Datasheet, PDF (17/36 Pages) Aeroflex Circuit Technology – CT2553 / 2554 / 2555 / 2556 Advanced Integrated MUX (AIM) Hybrid FOR MIL-STD-1553

15
76543210
00000001 1
CURRENT AREA B/A
T/R (from command word)
SUB-ADDRESS (command word)
Figure 20 – RTU Look-Up Address
RTU MESSAGE BLOCK TRANSFER SEQUENCE
RTU message transfer operations begin
automatically upon receipt of a valid command
word from the 1553 bus. A message transfer
takes the form of an RTU Start Of Message
(SOM) cycle followed by the 1553 Message
Transfer Cycle and an RTU End Of Message
(EOM) cycle (See Figure 22).
RECEIVED COMMAND WORDS
LOOK-UP
WORD TABLE (A)
T/R SUBADD COUNT ADDRESS
0 00000 XXXXX 0140
0 00001 XXXXX 0141
0 00010 XXXXX 0142
*
64 LOCATIONS
*
*
1 11110 XXXXX 017E
1 11111 XXXXX 017F
DATA BLOCK
DATA BLOCK
USER DEFINED
USER DEFINED
USER DEFINED
USER DEFINED
USER DEFINED
Figure 21 – Look-Up Table Example
1553 COMMAND WORD
RECEIVED
READ STACK POINTER
During the RTU SOM cycle, the CT2553 the
following actions:
1. Loads the 1553 command word.
2. Reads the current area Stack Pointer to get the
address of the current Descriptor Stack Entry
(DSE).
UPDATE DESCRIPTOR STACK
BLOCK STATUS WORD, TIME
TAG AND COMMAND WORD
READ LOOK-UP TABLE USING
T/R SUBADDRESS CURRENT
AREA BIT B/A
3. Stores an SOM flag into the Block Status Word
to indicate a transfer in progress.
4. Writes the Time Tag value into the the
Descriptor Stack.
5. Stores the Command Word received.
6. Reads the associated Data Block Address from
the (current area) Look-Up Table.
TRANSFER DATA TO/FROM
1553 INTERFACE DEVICE
MESSAGE COMPLETE
NO
?
YES
UPDATE BLOCK STATUS WORD
AND TIME TAG
The MESSAGE TRANSFER CYCLE refers to the
actual transfer of the 1553 message under control
of the CT2553. The CT2553 transfers data to and
from the memory on a word-by-word basis.
Upon completion of the message transfer, the
CT2553 executes an RTU End Of Message
(EOM) cycle during which the CT2553:
INCREMENT STACK POINTER
BY FOUR
GENERATE EOM INTERRUPT AND
ERROR INTERRUPT IF ERROR
CONDITION DETECTED
1. Generates an EOM or Error interrupt (if
enabled).
2. Updates the Block Status Word: clears SOM,
sets EOM, and any appropriate error bits.
3. Writes the Time Tag value into the Descriptor
Stack.
4. Increments the Stack Pointer by 4.
WAIT FOR NEXT
1553 COMMAND
Figure 22 – RTU Message Transfer
Operation
Aeroflex Circuit Technology
17
SCDCT2553 REV B 8/6/99 Plainview NY [phone]