MA28140 Datasheet, PDF (8/72 Pages) Dynex Semiconductor – Packet Telecommand Decoder

MA28140
State Number
S1
S2
S3
State Name
INACTIVE
SEARCH
DECODE
State Definition
All telecommand channels are inactive (no bit lock is achieved)
or no bit modulation is detected.
Incoming bit stream is searched, bit by bit, for the Start
Sequence pattern.
Codeblocks, which are either free of error or which can be
corrected, are received and decoded, and their information
octets are transferred to the layer above
Event Number
E1
E2 (a) (c)
(b)
E3
E4
Event Name
CHANNEL ACTIVATION
CHANNEL
DEACTIVATION
CLTU ERROR
START SEQUENCE
FOUND
CODEBLOCK
REJECTION
Event Definition
Bit modulation is detected and bit lock is achieved:
telecommand bit stream is present
Deactivation of the TC Active Signal
More than 37 codeblocks accepted in the CLTU
or Timeout on the TC Clock signal
or Activity on a channel having higher priority in priority mode
The Start Sequence pattern has been detected, signalling the
beginning of the first codeblock of the CLTU
A codeblock is found uncorrectable (erroneous codeblock or
tail sequence). No information octet from this codeblock is
transferred to the layer above
Codeblock transfer is performed in a serial way to the
above layer (Transfer layer). Two indication signals are
provided to the above layer - one indicating the whole frame
duration, the other asserted each time a 7 octets block is being
transferred.
The following rules apply to the data transfer between the
Coding Layer and the Transfer Layer:
• When the first Candidate Codeblock is affected by an
event E4 or by an event E2, the CLTU is abandoned. No
Candidate Frame is transferred to the Transfer Layer.
• When the first Candidate Codeblock is found to be error
free, or if it contained one error which has been corrected, its
information octets (i.e. 7 octets) are transferred to the
Transfer Layer. The decoding of the CLTU continues until
one of the following events occurs:
1- when an event E4 (codeblock rejection) occurs for any
of the 37 possible Candidate Codeblocks the decoder returns
to the search state S2 with the following actions:
- The codeblock is abandoned
- No information from that codeblock is transferred to
the layer above
- The Coding Layer indicates to the Transfer Layer the
end of transfer of the Candidate Frame.
2- when an event E2 (channel deactivation) occurs the
decoder returns to the inactive state (for the channel) with the
following actions:
- The CLTU is aborted,
- The CLTU is reported as abandoned,
- A signal is sent to the Transfer Layer to indicate that
the entire block of octets making up the Candidate
Frame must be erased.
3- When an event E2(b) (CLTU error) occurs, the decoder
returns to the search state with the following actions:
- The CLTU is aborted,
- The CLTU is reported as abandoned,
- A signal is sent to the Transfer Layer to indicate that
the entire block of octets making up the Candidate
Frame must be erased.
A CLTU error occurs in the following cases:
- More than 37 codeblocks have been accepted in the
CLTU,
- A timeout on the TC clock signal occurs,
- Activity on a channel having higher priority is
detected in priority mode.
The DECOD output is activated when the CLTU decoder
state is S3.
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