CT2553 Datasheet, PDF (19/36 Pages) Aeroflex Circuit Technology – CT2553 / 2554 / 2555 / 2556 Advanced Integrated MUX (AIM) Hybrid FOR MIL-STD-1553

MT OPERATION
Initiate a Reset in order to initialize the CT2553.
Configure the CT2553 as a Bus Monitor (MT) by
setting the appropriate Configuration Register
Bits. See Figure 24 for MT initialization Steps.
MT MEMORY CONFIGURATION. The user
configures the memory by writing the start
address for 1553 data storage into the Stack
Pointer location. The Monitor Stack will
automatically wrap around once the RAM has
been filled (i.e., location FFF(H) is followed by
location 0000). An example of a typical MT
Memory Map 4 given in Table 5.
Table 5 – Typical MT Memory Map
HEX ADDRESS
FUNCTION
0000
0001
0002
0003
0004
0005
0006
•
•
0100
•
•
FFFF
First Received 1553 Word
First Identification Word
Second Received 1553 Word
Second Identification Word
•
•
•
•
•
Stack Pointer (Fixed location)
•
•
•
MT START SEQUENCE. After setting the
CONTROLLER START bit in the Start/Reset
Register, the CT2553 takes the following actions:
1. Reads the start address for 1553 data storage
from the Stack Pointer location. The Stack
Pointer location(s) will be overwritten with 1553
data once the MT mode has begun and 1553
data is written into locations 0100(H) and
0101(H)].
2. Stores the received 1553 word into memory.
3. Increments the Stack Pointer by 1.
4. Generates an Identification Word and stores
this value into memory.
5.Repeats steps 2-4 until a Reset condition
occurs.
MT IDENTIFICATION WORD. The Identification
word provides the CPU with information pertaining
to the received 1553 word. Its format is shown in
Figure 25, This information allows the user to
analyze the 1553 data.
THIS-RT: Each command appearing on either
1553 Bus is decoded and tested for
Manchester/protocol errors. If the CT2553
receives a valid command word containing a
Command Sync and a RTU address equivalent to
the RTAD0-RTAD4 inputs (pins 10, 9, 50, 49, and
11, respectively), THIS-RT (pin 55) will be pulsed
low. This signal can be used to identify specific
1553 commands or for switching to RTU mode
upon receipt of a command to this address.
START
ISSUE RESET COMMAND
CLEAR RAM
INITIALIZE STACK POINTER
SET CONFIGURATION
REGISTER TO MT MODE
ISSUE START COMMAND
Figure 24 – MT Initialization
MSB
15
GAP TIME
WORD FLAG
THIS RT
BROADCAST
ERROR
COMMAND SYNC
1553 CHANNEL A/B
CONTIGUOUS DATA
MODE CODE
LSB
876543210
1
BIT NAME
DEFINITION
GAP TIME
WORD FLAG
THIS RT
BROADCAST
ERROR
COMMAND SYNC
1553 CHANNEL
A/B
CONTIGUOUS
DATA
MODE CODE
Indicates the time between receipt of the
previous and current words.Time is
indicated in 0.5µs increments for a
maximum of 128 µs and goes to FF over
128µs. (See Word Gap bit.)
Always logic 1.
Logic 0 indicates RT address field of the
associated command or Status Word
matches the RT address field of the
CT2553.
Logic 0 indicates the RTU address field of
the command or Status Word
corresponds to address 31 (decimal).
Logic 1 indicates Manchester, Parity,
Sync and/or low bit counter.
Logic 1 indicates 1553 Command or
Status Word sync field. (Logic 0 indicates
a Data Word sync field in received word.)
Indicates word received on 1553 Bus A
(1) or Bus B (0).
Logic 1 indicates the word was received
within 2µs of the previous word. If logic 0,
bits 8-15 contain the measured gap
between the words.
When logic 1, the data transferred is a
mode code command.
Figure 25 – MT Identification Word
Aeroflex Circuit Technology
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SCDCT2553 REV B 8/6/99 Plainview NY [phone]