act7006 Aeroflex Circuit Technology, act7006 Datasheet - Page 12

• Manufacturer Part Number: act7006
• Description: Act7005/7006 Single Package Solution Dual Transceiver, Protocol, Subsystem
• Manufacturer: Aeroflex Circuit Technology

described below are available and are essentially
independent. Any, all, or none may be selected.
Also, reporting of faults by the subsystem requires
that SSERR be latched (not pulsed) low until the
fault is cleared.
Resetting SSF and TF on Receipt of Valid
Commands
lines are held high, then the Status Word Register
will be reset on receipt of any valid command with
the exception of Transmit Status and Transmit Last
Command. Note that in this mode, the TF will never
be seen in the Status Word, and the SSF will only be
seen if SSERR is latched low. Also note that the SSF
will not be seen in response to Transmit Status or
Transmit Last Command if the preceding Status
Word was clear, regardless of actions taken on the
SSERR line after the clear status transmission.
Status Register Update at Fault Occurrence
TF or SSF will appear in response to a Transmit
Status or Transmit Last Command issued as the first
command after the fault occurs. Any other command
(except as noted in the Preserving the BIT Word
section) will reset the TF and SSF. Repeated
Transmit Status or Transmit Last Command
immediately following the fault will continue to show
the TF and/or SSF in the Status Word. Note that this
behavior may not meet the "letter-of-the-spec" as
described in MIL-STD-1553B, but is considered the
"preferred" behavior by some users.
TF and SSF Reporting in the Next Status
Word – After the Fault
or SSF will appear in response to the very next valid
command after the fault except for Transmit Status
or Transmit Last Command. The flag(s) will be reset
on receipt of any valid command following the status
transmission with the flag(s) set except for Transmit
Status, Transmit Last Command, or as noted in the
following section on Preserving the BIT Word.
Preserving the BIT Word
Subsystem Handshake Failure, and Loop Test
Failure Bits in the BIT Word, it is necessary to select
BIT DECODE (hold it low). This will prevent resetting
those bits if the Transmit Bit Word Mode Command
immediately follows the fault or follows a Transmit
Last Command or Transmit Status immediately
following the fault. It will also prevent resetting the TF
and SSF Bits in the Status Word. Any other valid
commands will cause those BIT Word Bits and the
Status Word Bits to be reset.
If ENABLE is selected and the other three option
If STATUS UPDATE is selected (held low), then the
If NEXT STATUS is selected (held low), then the TF
In order to preserve the Transmitter Timeout Flag,
Aeroflex Circuit Technology
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SCD7005 REV B 8/2/01
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