SI2107 SILABS [Silicon Laboratories], SI2107 Datasheet - Page 28

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

Si2107/08/09/10
When the sequence has completed, the device clears
the LNB sequence start bit, LNBS, automatically. Note
that, when operating in this mode, the DRC pin is high
while transmitting and low while receiving.
The DiSEqC message uses the LNBS bit to start
transmission and behaves the same as in Automatic
LNB Messaging Mode. However, the guard intervals
between each signaling method (LNB voltage change,
DiSEqC message, tone burst, and continuous tone
resumption) are controlled by the host.
In this mode, the tone burst should be implemented by
using a 1-byte DiSEqC message of all 0s or all 1s
programmed into FIFO1. The device uses appropriate
modulation for the tone burst; i.e., when FIFO1 is
programmed to 00h (rather than a DiSEqC-compliant
modulation for a '00h' byte), no tone is generated. Also,
the device does not expect a reply if FIFO1 is
programmed to FFh; i.e., the assertion of bit7 is not
considered a request for the peripheral to reply in step-
by-step LNB messaging mode.
6.7.4.3. Manual LNB Messaging Mode
The manual LNB messaging mode provides the
maximum level of signaling flexibility but at the expense
of increased software interaction. The device is
configured in this mode by appropriately programming
the LNBM register. The continuous tone, tone burst, and
messaging controls are not functional in this mode.
When the tone format bit, TFS, is programmed for use
of the internal oscillator, assertion of the TT bit
modulates the output of the internal tone generator on
the TGEN pin, and the TR bit records the envelope of a
tone presented to the TDET pin.
28
End of continuous
tone (if present)
> 15ms
Change of voltage
(if required)
reply requested)
1st message (no
> 25ms
Figure 16. LNB Signaling Sequence
(reply requested)
2nd message
Preliminary Rev. 0.7
6.7.4.2. Step-by-Step LNB Messaging Mode
By appropriately programming the LNB Messaging
Mode register, LNBM, the device allows for individual
control of each signaling method by the host. In this
mode, the LNB voltage, LNBV, and LNB continuous
tone enable, LNBCT, take effect once they are set
without waiting for the user to set the LNB sequence
start bit, LNBS.
When the tone format select bit, TFS, is programmed to
use an external oscillator, the TT bit directly controls the
output of the TGEN pin, and the TR bit directly reflects
the input of the TDET pin. In this mode, the tone
direction control bit, TDIR, directly controls the output of
the DRC pin.
6.8. On-Chip LNB DC-DC Step-Up
In addition to the LNB signaling controller present on all
device versions, Si2108 and Si2110 devices contain an
internal supply controller circuit. This internal dc-dc
controller can be enabled via register bit LNB_EN. The
internal circuit requires the connection of an external
circuit with a specified bill-of-materials, and this
combination generates the selected LNB voltage with
superimposed one-way or two-way LNB signaling
communications. Si2108/10 devices include short-
circuit protection, overcurrent protection, and a step-up
dc-dc controller to implement a low-cost LNB power
supply using minimal external components. The
required circuit for DiSEqC1.x operation is illustrated in
Figure 5 on page 11. A circuit for DiSEqC2.x operation
is shown in Figure 6 on page 12.
When the LNB supply circuit is populated, the Si2108/
10 detects a connection to ground on the ISEN pin via
R10 during reset and configures the LNB pins for dc-dc
converter control instead of providing the interfaces to
an external LNB supply regulator discussed in the
previous section. See Table 17.
Controller (Si2108/10 Only)
< 150ms
Reply to 2nd
message
> 15ms
Tone Burst
> 15ms
Start of continuous
tone (if present)