CT2577 Datasheet, PDF (7/41 Pages) Aeroflex Circuit Technology – APPLICATION NOTE 108

NSYNC
NVCR
NDATA
NILLCMD
Signal to subsystem indicating receipt of a Synchronize mode commands If the mode
code has an associated data word, it will be available on T0-T15 at this time. If there
is no associated data word, T0-T15 will be zero.
Early indication that a Command Word has been received and is being processed.
The Command Word received is available on the T0-15 bus for decoding at this time.
The user can use this signal for message illegalization and to set the RT Status bits.
Access to valid data word in real time before being written to RAM. Data word
available on T0-T15 during active low signal.
Input to illegalise a command to the Remote Terminal with a clear status response.
The signal is sampled after NVCR except non mode code receive commands in
which case it is sampled after the last data word has been received. A low on this
input will illegalise the message, Command will not be stored in the Command /
Status memory and no transfers to / from main RAM will take place. The device will
respond with a clear status unless a bit has been specifically set. No data will be
transmitted following status.
BC Discrete Signals
NNEWBUS
A Bus Control sequence may not normally be initiated until the current sequence is
completed, indicated by signal EOT. However, the Bus Control sequence may be
terminated and restarted if NNEWBUS is active low along with write to address 0 00
00 (000h). This feature would only be used in bus switching.
EOT
Indicates that a valid transfer has been completed on the bus selected.
1 = Valid transfer completed
0 = Not yet Completed
ERROR
Indication that an error has occurred either in the information transferred to the unit
from the subsystem or in the transfers on the 1553 data bus. Nature of error is
available by reading from register location 0 00 12 (012h).
1 = Error has occurred
0 = No error
NSTSTRB
This signal goes low for 8.5 uS to indicate a valid transfer has been completed on the
1553 data bus and the received Status word is now available on the T0-T15 highway.
The Status word is also stored in the Command / Status memory at this time. Once
the signal goes high data received by the Bus Controller (RT to BC transfer) will be
transferred to the main RAM from the 32 word data buffer memory. Note: Data
transferred in RT to RT transfers is not stored in the Bus Controllers main RAM.
NNINHST
May be used to illegalise a message just received. Signal can be tied to STATUS for
illegalisation due to 1760 checksum failures. A low will prevent any data received
being transferred to the main RAM, and the Status word will not be stored in the
Command / Status memory.
APPLICATION NOTE #108
7
Released 9/98