![](http://datasheet.mmic.net.cn/Silicon-Laboratories-Inc/SI3019-F-GM_datasheet_102091/SI3019-F-GM_30.png)
Si3050 + Si3011/18/19
30
Rev. 1.5
Figure 22. Typical Application Circuit for
Ground Start Support on the SI3050
5.14.1. Ground Start Idle
Ensure the relay in series with TIP is closed by clearing
the TGOE bit (Register 32, bit 1). This enables the DAA
to sense if the CO grounds TIP. Set RG to 1
(Register 32, bit 0) so that no current flows through the
relay connecting RING to ground.
5.14.2. DAA Requests Line Seizure
With TGOE set to zero, seize the line by closing the
relay
in
series
with
RING
(clear
the
RG
bit,
Register 32, bit 0). The CO detects this current flowing
on RING and grounds TIP. This sets the TGD bit
(Register 32, bit 2). The DAA may then be taken
off-hook and the relay in series with RING opened (clear
the RG bit). The call continues as in loop-start mode.
5.14.3. CO Requests Line Seizure
In a normal on-hook state, the relay in series with TIP
should be closed, connecting the –24 V isolated supply.
The CO grounds TIP to request line seizure, causing
page 30) detects this current and sets the TGD bit
(Register 32, bit 2). This bit remains high as long as
current is detected. The TGDI bit (Register 4, bit 1) is a
sticky bit, and remains high until cleared. A hardware
interrupt on the AOUT/INT can be made to occur when
TIP current begins to flow by enabling the TGDM bit
(Register 3, bit 1). Clear the interrupt by writing 0 to the
TGDI bit (Register 4 bit 1). The DAA may then be taken
off-hook and the call continued as in loop-start mode.
5.15. Interrupts
The AOUT/INT pin can be used as a hardware interrupt
pin by setting the INTE bit (Register 2, bit 7). When this
bit is set, the analog output used for call progress
monitoring is not available. The default state of this
interrupt output pin is active low, but active high
operation can be enabled by setting the INTP bit
(Register 2, bit 6). This pin is an open-drain output
when the INTE bit is set and requires a 4.7 k
pullup or
pulldown for correct operation. If multiple INT pins are
connected to a single input, the combined pullup or
pulldown resistance should equal 4.7 k
Bits 7–0 in
Register 3 and bit 1 in Register 44 can be set to enable
hardware interrupt sources (bit 0 is available with the
Si3011 and Si3019 line-side devices only). When one or
more of these bits is set, the AOUT/INT pin goes into an
active state and stays active until the interrupts are
serviced. If more than one hardware interrupt is enabled
in Register 3, use software polling to determine the
cause of the interrupts. Register 4 and bit 3 of
Register 44 contain sticky interrupt flag bits. Clear these
bits after servicing the interrupt.
Registers 43 and 44 contain the line current/voltage
threshold interrupt. These line current/voltage registers
and interrupt are only available with the Si3011 and
Si3019 line-side devices. This interrupt is triggered
when the measured line voltage or current in the LVS or
LCS2
registers,
as
selected
by
the
CVS
bit
(Register 44, bit 2), crosses the threshold programmed
into the CVT[7:0] bits. With the CVP bit, the interrupt
can be programmed to occur when the measured value
rises above or falls below the threshold. Only the
magnitude
of
the
measured
value
is
used
for
comparison to the threshold programmed into the
Table 15. Component Values for the Ground
Start Support Schematic
Symbol
Value
Supplier(s)
R101
200
, 2 W, ±5%
Venkel, SMEC,
Panasonic
R102, R103,
R106
1k
, 1/10 W, ±5% Venkel, SMEC,
Panasonic
R104
1.5 k
, 1/10 W, ±5% Venkel, SMEC,
Panasonic
R105
10 k
, 1/2 W, ±5% Venkel, SMEC,
Panasonic
RL1
AQW210S
Aromat, NEC
U3
PS2501L-1
NEC, Fairchild
VD
-24V
VD
TIP
RING
TGDb
RGb
TGDEb
RL1
Opto-Relay
1
2
3
4
5 5
6 6
7 7
8 8
U3
Opto-Isolator
1
2
3 3
4 4
R105
R101
R102
R103
R104
R106