AN332
150
Confidential Rev. 0.2
Command 0x54. WB_SAME_STATUS (Si4707 Only)
Retrieves SAME information, acknowledges SAMEINT interrupts and clears the message buffer. The command
indicates whether the start of message, end of message or preamble is detected and if the header buffer is ready.
The state of the decoder, message length, and 8 bytes of the message buffer with corresponding confidence level
is returned. The byte at address 0 will be the first byte following the header block identifier "ZCZC", typically "-"
(Dash). Each byte has an associated confidence metric ranging from 0 (low confidence) to 3 (high confidence).
Command Arguments: Two
Response Bytes: Thirteen
Command
Bit
D7
D6
D5
D4
D3
D2
D1
D0
CMD
0
1
0
1
0
1
0
0
ARG1
0
0
0
0
0
0
CLRBUF
INTACK
ARG2
READADDR[7:0]
Arg
Bit
Name
Function
1
1
CLRBUF
Clear Buffer
0 = Message Buffer preserved.
1 = Clears the contents of the SAME Message Buffer.
Clears the contents of the SAME Message Buffer if set. The buffer will
always be cleared during WB_TUNE_FREQ. If the buffer is not cleared then
each message received will be combined with the previously received mes-
sage to increase the certainty of the message content. After receipt of an
End-of-Message, this buffer must be cleared by the user. To prevent different
headers from being combined into an incorrect message, the user must clear
the buffer before a new header is transmitted. As there is no indication that a
new header is about to be transmitted, the user must rely on other events to
indicate when to clear the buffer. The buffer should be cleared after receipt of
three headers, after the end-of-message marker, when the 1050 Hz alert
tone has been detected or 6 seconds after the reception of the last header
was completed and no new preamble has been detected. Once the buffer
has been cleared, it will remain empty until the next start-of-message is
received. Alternatively, the user may clear the buffer after each header is
received and rely on a traditional best 2-of-3 voting method. In this case, no
message combining is performed.
1
0
INTACK
Interrupt Acknowledge
0 = Interrupt status preserved.
1 = Clears SAMEINT.
2
[7:0]
READADDR[7:0]
Byte in the message buffer to start reading from. Note that 8 bytes will always
be returned, however the WB_SAME_STATUS:MSGLEN will report the total
length of the message and the user must disregard bytes past this length.
