369
12.4.6
Receiver Shutdown Packet
The contents of this section apply to the FLEX Roaming Decoder. They are not applicable to
the FLEX Non-Roaming Decoder.
The Shutdown Packet is sent in both synchronous and asynchronous mode. It is designed to
indicate to the host that the receiver is turned off and how much time there is until the FLEX
decoder will automatically turn it back on.
Table 12-27 Receiver Shut Down Packet Bit Assignments
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Byte 3
0
1
1
1
1
1
1
1
Byte 2
FNV
CF
6
TNF
6
NAF
6
CF
5
TNF
5
NAF
5
CF
4
TNF
4
NAF
4
CF
3
TNF
3
NAF
3
CF
2
TNF
2
NAF
2
CF
1
TNF
1
NAF
1
CF
0
TNF
0
NAF
0
Byte 1
TNF
7
FCO
Byte 0
FNV:
Frame Number Valid. This bit is set if the last decoded frame info word was correctable and
the frame number was the expected value. When in asynchronous mode, this value will be 0.
CF:
Current Frame. When in synchronous mode, this is the current frame number. This value is
latched on the negative edge of the
READY
line when this packet is sent to the host. The value of
this field is valid only if the FLEX decoder is in synchronous mode and the FIV bit in the status
packet is set. When in asynchronous mode, this value will be 0.
TNF:
Time to Next Frame. When in synchronous mode TNF indicates the time to the start of the
A-word check if the FLEX decoder were to warm up for the next frame. When in asynchronous
mode TNF indicates the time to the start of the next automatic noise detect. See “Using the
Receiver Shutdown Packet” on page 66 for an explanation on how to use this value. This value is
latched on the negative edge of the
READY
line when this packet is sent to the host.
FCO:
Frame Carried On. Set if the FLEX decoder is decoding the next frame due to the reception
of a non-zero carry-on value in the current or a previous frame. When in asynchronous mode, this
value will be 0.
NAF:
Next Assigned Frame. This is the frame number of the next frame the FLEX decoder was
scheduled to decode when the receiver shut down. The value of this field is valid only if the FLEX
decoder is in synchronous mode and the FIV bit in the status packet is set. When in asynchronous
mode this value will be 0.