A N 9 3
116
Rev. 1.4
When DCR = 1, the device presents a dc line impedance of 800
,
which can be used to enhance operation with a
parallel phone, for improved low line voltage performance, and for overload.
This bit must be set to 0 when the
modem is on-hook.
See "6.2.1. DC Termination" on page 145 for details.
Bit 6 (OHS) is used to control the speed with which the modem drops the line. The default setting, OHS = 0,
causes the modem to go from the off-hook state (drawing loop current) to the on-hook state (not drawing loop
current) quickly. This operation is acceptable in many countries. However, some countries, such as Italy, South
Africa, and Australia, have spark quenching requirements. Spark quenching can be accomplished by placing a
resistor and a capacitor across the hookswitch or by controlling the off-hook to on-hook transition speed to prevent
excessive voltage buildup. Slowly reducing the loop current to zero fulfills the spark quenching requirement without
the extra components. Setting OHS = 1 causes the hookswitch to turn off the loop current with a ramp instead of a
step.
Bits 3:2 (DCV) select the dc termination for the modem. DCV = 00 is the lowest voltage mode supported on the
ISOmodem. DCV = 01 is the next lowest voltage mode. See "6.2.1. DC Termination" on page 145 for details.
Bit 1 (RZ) = 0 (default) allows ringer impedance to be determined by external components. This impedance is
typically 800–900 k
. RZ = 1 enables on-chip synthesis of a lower ringer impedance for countries, such as Poland,
South Africa, and South Korea.
Bit 0 (RT), Ring Threshold, is used to satisfy various country ring detect requirements. RT = 0 (default) sets the ring
threshold for 11–22 V
RMS
. RT = 1 sets the ring threshold for 17–33 V
RMS
. Signals below the lower level of the
range are not detected. Signals above the upper level of the range are always detected.
Содержание Si2404
Страница 2: ...AN93 2 Rev 1 4 ...
Страница 27: ...AN93 Rev 1 4 27 Figure 7 Parallel Interface Read Timing Figure 8 Parallel Interface Write Timing ...
Страница 200: ...AN93 200 Rev 1 4 Figure 31 TAM Handset and Speakerphone Voice Paths ...
Страница 201: ...AN93 Rev 1 4 201 Figure 32 Si3000 Codec Gain and Signal Selection Options ...
Страница 290: ...AN93 290 Rev 1 4 Figure 57 256 Band Spectral Display Figure 58 2048 Band Spectral Display ...
Страница 305: ...AN93 Rev 1 4 305 Figure 76 Parallel or SPI Port Interrupt Service Flowchart ...