si3200-x-gs Silicon Laboratories, si3200-x-gs Datasheet - Page 45

• Manufacturer Part Number: si3200-x-gs
• Description: Dual Programmable Cmos Slic With Line Monitoring
• Manufacturer: Silicon Laboratories

4.12.1. Polarity Reversal
The Si3232 supports polarity reversal for message-
waiting functionality as well as various signaling modes.
The ramp rate can be programmed for a smooth
transition or an abrupt transition to accommodate
different application requirements. A wink function is
also provided for special equipment that responds to a
smooth ramp to V
register bits required to program the polarity-reversal
modes.
An immediate reversal (hard reversal) of the line polarity
is achieved by setting the Linefeed register to the
opposite polarity. For example, a transition from
Forward Active mode to Reverse Active mode is
achieved by changing LF[2:0] from 001 to 101. Polarity
reversal can also be accommodated in the OHT and
ground-start modes. The POLREV bit is a read-only bit
that reflects whether the device is in polarity reversal
mode. A smooth polarity reversal is achieved by setting
Linefeed
Polarity Reversal Status
Wink Function
(Smooth transition to Voc = 0 V)
Smooth Polarity Reversal Enable
Smooth Polarity Reversal Ramp
Rate
Table 27. Register and RAM Locations used for Polarity Reversal
Parameter
OC
= 0 V. Table 27 illustrates the
See Table 12
Read only
1 = Ramp to 0 V
0 = Return to previous V
0 = Disabled
1 = Enabled
0 = 1 V/125 µs
1 = 2 V/125 µs
Programmable Range
Preliminary Rev. 0.96
the PREN bit to 1 and setting the RAMP bit to 0 or 1
depending on the desired ramp rate (see Table 27).
Polarity reversal is then accomplished by toggling the
linefeed register from forward to reverse modes as
desired.
A wink function is used to slowly ramp down the TIP-
RING voltage (V
original VOC value (set in the VOC RAM 0 location).
This scheme is used to light a message-waiting lamp in
certain handsets. To enable this function, no change to
the linefeed register is necessary. Instead, the user
must set the VOCZERO bit to 1 to cause the TIP-RING
voltage to collapse to 0 V at the rate programmed by the
RAMP bit. Setting the VOCZERO bit back to 0 causes
the TIP-RING voltage to return to its normal setting. A
software timer provided by the user can automate the
cadence of the wink function. Figure 23 illustrates the
wink function.
OC
Register/RAM Bits
OC
VOCZERO
POLREV
) to 1 followed by a return to the
LF[2:0]
RAMP
PREN
LINEFEED
Location
POLREV
POLREV
POLREV
POLREV
Si3232
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