CT2553 Datasheet, PDF (11/36 Pages) Aeroflex Circuit Technology – CT2553 / 2554 / 2555 / 2556 Advanced Integrated MUX (AIM) Hybrid FOR MIL-STD-1553

Table 2 – CT2553 Register Address Definition
Address Bits
A2 A1 A0
Definition
0 0 0 R/W Interrupt Mask Register
0 0 1 R/W Configuration Register
0 1 0 – Not Used
0 1 1 W Start/Reset Register
1 0 0 R/W * External Register
1 0 1 R/W * External Register
1 1 0 R/W * External Register
1 1 1 R/W * External Register
* Note: R/W (read/write) capability is dependent on the user's
decoding implementation (See Figure 9).
CONTENTION HANDLING
The CT2553 arbitrates shared RAM (and control
register) accesses between the host CPU and the
internal 1553 protocol logic.
If the host attempts to access the RAM while an
internal 1553 memory cycle is in progress, the
CT1553 will delay the CPU's memory cycle by
inserting wait states via the READYD control
signal until the cycle has been completed. The
maximum delay is 1.8µs.
If the internal 1553 protocol logic attempts to
access the RAM while the host CPU has control of
the memory, the internal 1553 logic will wait until
the host CPU cycle has been completed. To
ensure the integrity of 1553 data transfers, the
host CPU must complete its memory cycle within
1.5µs (See Figures 28-32).
SELF TEST
The CT2553 has two self-test modes: the
automatic, continuous On-Line test and the
software-initiated Off-Line test. In both tests the
Loop Test Fail bit within the Block Status Word will
be set to a logic 1 if a failure is detected.
ON-LINE TEST. The On-Line test occurs in BC
and RTU modes during transmission of each
message onto the 1553 bus. This test wraps
around the last word transmitted, exercising the
1553 protocol logic through the 1553 transceivers.
While operating as a BC, the last word transmitted
is received, decoded, and written back into
memory location immediately following the last
word within the message block. The host CPU can
read and compare this Loop Back Word with the
last word of the message Data Block; these two
words should be identical. This insures data
integrity between the CPU and the CT2553.
While in the RTU mode, the internal 1553 Status
Word will be updated to reflect the result of the self
test. The Status Word's Terminal Flag bit will be
set to a logic 1 if a fault was indicated by the
wrap-around, self-test.
OFF-LINE TEST. The software-initiated Off-Line
test can be executed only when the CT2553 is
configured as a BC. Set the Wrap-Around Test bit
within the BC Control Word to a logic 1 and initiate
any standard message transfer. This inhibits the
1553 transceivers and initiates the standard
wrap-around test (i.e., internal 1553 encoder
output is fed back into the decoder - the word is
then written into memory). See BC Operation and
Figure 14, BC Control Word for more details.
15
876543210
NOT USED
BUS CHANNEL A/B
OFF-LINE SELF TEST
MASK BROADCAST
NOT USED
MODE CODE
BROADCAST
RT-RT
BIT NAME
DEFINITION
BUS CHANNEL Determines whether message will be
A/B
transmitted on 1553 Bus A or Bus B.
Logic 1 = A, logic 0 = B.
INITIATE
OFF-LINE SELF
TEST
Logic 1 performs internal off-line
transmit/receive test. The last word
of the message is looped back
through the decoder and placed in
RAM. See Self Test paragraph.
MASK
BROADCAST (1)
When logic 1, prevents Broadcast
RCVD bit of the 1553 Status Word
response from signalling a status
error as a result of a Broadcast
command. (A FORMAT error will be
generated if the BROADCAST bit is
not set on the RTU’s Status Word.)
MODE CODE
When logic 1, the message is treated
as a Mode Code. (The Command
Word - Word Count field indicates
Mode Code type.)
BROADCAST
When logic 1, indicates that the
message is a Broadcast Command.
(No Status Word is expected.)
RT-RT
When logic 1, the message is treated
as an RT-RT transfer. (The next two
words are Command Words.) Both
Status Word responses are
validated.
Note:
1. MASK BROADCAST XOR BROADCAST BIT in Status Word =
STATUS SET ERROR.
2. When the BC expects the BROADCAST bit set in the Status Word,
a logic 1 will mask the Status Interrupt Error flag.
Figure 14 – BC CONTROL WORD
RESET
The CT2553 can be reset by pulsing the
MSTRCLR (pin 71) low or by writing to the
Start/Reset register. After a reset condition has
occurred, the Configuration, Interrupt, and
(internal) Block Status word register outputs are
forced to a logic 0.
Aeroflex Circuit Technology
11
SCDCT2553 REV B 8/6/99 Plainview NY [phone]