CT2553 Datasheet, PDF (8/36 Pages) Aeroflex Circuit Technology – CT2553 / 2554 / 2555 / 2556 Advanced Integrated MUX (AIM) Hybrid FOR MIL-STD-1553

15
EOM
SOM
CHB/CHA
(RTU ONLY)
ERROR FLAG
87
0
11111 111
STACK POINTER. A STACK POINTER (SP) is
maintained at a specified location in shared RAM
for each Descriptor Stack (SP-A: 0100H; SP-B:
0104H). Each Stack Pointer must be initialized by
LOOP TEST FAIL
the CPU to point to the Descriptor Stack Entry to
RESPONSE TIME OUT (BC ONLY) ^{be used for the first MIL-STD-1553 transmission.}
FORMAT ERROR
STATUS SET (BC ONLY)
The current area SP is automatically incremented
by four following each message transfer thereby
always pointing to the next Block Status Word.
Note: In BC operation, the CT2553 always writes the BSW to RAM with
Bit-13. CHB/CHA toggles as per the message control word setting.
BIT NAME
DEFINITION
EOM
Set at the completion of a message
transfer regardless of whether any errors
were detected.
SOM
CHB/CHA
Set at the beginning of a message transfer
and Reset upon completion of the transfer.
Set in RTU mode to indicate whether the
message was received on 1553 bus A or
bus B. Toggles to indicate channel, in BC
mode.
ERROR
FLAG
Indicates that an error was detected within
the message transfer. The specific error
condition(s) are identified in bits 8-11.
Note: The Stack Pointer is maintained internally using an
8-BIT REGISTER for the HIGH BYTE and an 8-BIT
COUNTER for the LOW BYTE. The high byte remains
constant (user value) while the low byte will wrap around
from FF(H) to 00(H). For example: a current Stack Pointer
value of 00 FF(H) will increment to 00 00(H) and not
01 00 (H).
LOOK-UP TABLE (RTU). A data block address
Look-Up Table is used to indicate the data blocks
to be used for individual commands. Look-Up is
based upon the T/R (transmit/receive) and
Subaddress bits of the received 1553 Command
Word. See RTU Operation for detailed operation;
two tables are provided for double buffering in the
RTU mode.
STATUS SET
Set in BC mode to indicate that a status
flag bit was set within the received RTU
Status Word or that the RTU address did
not match the associated Command. Set
in BC mode when the message error bit is
set within the received RTU Status Word.
FORMAT
ERROR
Also set in RTU mode (RT-RT transfer;
CT2553 is acting as the receiving RT)
when the transmitting RTU Status Word
contains an incorrect address. Also, set in
BC or RTU mode if the message violates
MIL-STD-1553 (parity, Manchester, sync
bit count, non-contiguous data or word
count errors).
MULTIPLE BUFFERING (BC/RTU). Unused
areas of shared RAM can be used to store
additional stacks, tables, data blocks and/or user
(non 1553-related) data. In this way, multiple data
blocks (RTU) or messages (BC) can be stored for
later use: simply update respective pointers and
initiate the appropriate start conditions. (BC mode
requires SP, message block address and message
count updating while in RTU mode, the SP and
Look-Up Table entry must be updated).
RESPONSE
TIMEOUT
Set in BC mode if the addressed RTU did
not respond within 14µs. Also set when
acting as a receiving RT (RT-RT transfer) if
the transmitting RT does not respond in
the specified 1553 response time.
LOOP
Set when the CT2553 does not pass the
TEST FAIL ^{Loop Test. See Self Test paragraph.}
Figure 8 – Descriptor Stack - Block Status
Word
The contents of the fourth word of the stack entry
depends upon the 1553 operating mode selected.
In BC mode, It contains the address of the
associated 1553 message (Data Block). In RTU
mode, it contains the complete (received) 1553
Command Word.
CT2553 REGISTERS
The CT2553 is controlled through the use of three
internal registers: Interrupt Mask Register,
Configuration Register and a Start/Reset Register.
In addition, the CT2553 can access up to four
external, user supplied registers (See Table 2).
Possible external register applications include:
CPU Time Tag storage and RTU Address
assignment (See Figures 9 and 10).
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