SI2107 SILABS [Silicon Laboratories], SI2107 Datasheet - Page 27

• Manufacturer Part Number: SI2107
• Description: SATELLITE RECEIVER FOR DVB-S/DSS
• Manufacturer: SILABS [Silicon Laboratories]

6.7.3. DiSEqC™
The DiSEqC signaling method extends the functionality
of the legacy 22 kHz tone by superimposing a
command protocol and adding an optional return
channel. A DiSEqC command normally consists of a
framing byte, an address byte, a command byte, and,
optionally, one or more data bytes. This format is
illustrated in Figure 13.
The length of a message is specified by MSGL. When
the message length is set to one byte, the message is
modulated using tone burst modulation. When the
message length is set to two or more bytes, the
message
modulation, and the odd parity bit is automatically
added. The DiSEqC modulation scheme is illustrated in
Figure 14.
6.7.3.1. DiSEqC 1.x One-Way Communication
Messages are programmed directly into the device
using a message FIFO that consists of six byte wide
registers, FIFO1–6. The messages must be written in a
first-in-first-out manner such that the first byte of a
message is stored in FIFO1; the second byte is stored
in FIFO2, and so on. If messages are longer than six
bytes, the device asserts the FIFO empty indicator, FE,
as soon as the sixth byte has been read. The LNB
control module then takes its next byte from FIFO1 and
continues the process. The message length must also
be reprogrammed to indicate how many more bytes
remain to be sent. The interval between FIFO reads is
typically 13.5 ms.
To support cascaded DiSEqC devices, it may be
necessary to repeat commands. Repeated commands
should be separated by at least 100 ms to ensure that
the far-end device is connected to the signaling path. To
facilitate the required 100 ms delay, a four byte
command
commands.
FRAMING
Figure 14. DiSEqC Compliant Modulation
Figure 13. DiSEqC Message Format
1.0 ms
'0' Data Bit
is
can
P
modulated
ADDRESS
be
0.5 ms
inserted
P
using
COMMAND
0.5 ms
'1' Data Bit
between
DiSEqC-compliant
P
1.0 ms
DATA
repeated
Preliminary Rev. 0.7
P
6.7.3.2. DiSEqC 2.x two-way communication
Two-way communication is supported via DiSEqC 2.x-
compliant messages. When the seventh bit in the
framing byte of an outgoing message is set to 1, the
device anticipates a response and monitors the line for
up to 150 ms for an incoming message. If no message
is detected during the 150 ms monitoring period, the
MSGTO bit is asserted to indicate the time-out
condition. A DiSEqC reply message typically consists of
a single framing byte and optionally one or more data
bytes as shown in Figure 15.
When a complete message has been received (one or
more bytes followed by 4 ms of silence), the MSGR bit
is asserted. Should parity errors exist in the received
message, the MSGPE flag is also asserted. If the
received message is longer than 6 bytes, the FIFO full
bit, FF, is asserted to indicate that a byte has been
written to FIFO6. The LNB control module writes the
next byte to FIFO1. The length of the received message
is recorded in the MSGRL register.
6.7.4. LNB Signaling Modes
6.7.4.1. Automatic LNB Messaging Mode
The Si2107/08/09/10 LNB Signaling Controller can fully
manage the generation and sequencing of all LNB
commands. The device is configured in this mode by
appropriately programming the LNB Messaging mode
register, LNBM. To initiate a message sequence, the
user should first program LNB voltage selection (LNBV),
continuous tone enable (LNBCT), tone burst type
(LNBB), and DiSEqC message parameters (MMSG,
MSGL,
sequence start bit, LNBS, must be set to start the
automated
automatically allocates the required delays between
each signaling method. Prior dc voltage levels and
continuous tones, if present, persist until the sequence
is initiated. A typical sequence is shown in Figure 16.
Multiple messages can be sent in a sequential manner
by setting the MMSG bit. When this bit is set, the LNB
control module delays continuous tone and tone burst
commands until all messages in the sequence have
been sent. After the current message is transmitted, the
MMSG bit is automatically cleared. The tone burst can
be disabled as part of this sequence depending on the
setting of BRST_DS.
FRAMING
and
Figure 15. DiSEqC Reply Format
transmission
FIFO1..6).
P
Si2107/08/09/10
DATA
Subsequently,
sequence.
P
DATA
The
the
device
LNB
P
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