si2401 Silicon Laboratories, si2401 Datasheet - Page 61
si2401
Manufacturer Part Number
si2401
Description
V.22bis Isomodem With Integrated Global Daa
Manufacturer
Silicon Laboratories
Datasheet
1.SI2401.pdf
(76 pages)
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SEE (RVC3). Ring Validation Control 3
Reset settings = 0001_0110 (0x16)
Bit
7:4
3:0
Name
Type
Bit
RMX[3:0]
RTO[3:0]
Name
D7
Ring Timeout.
These bits set when a ring signal is determined to be over after the most recent ring
threshold crossing.
RTO[3:0]
0000
0001
0010
.
.
.
1111
Ring Assertion Maximum Count.
These bits set the maximum ring frequency for a valid ring signal. During ring qualification,
a timer is loaded with the RAS[5:0] field upon a TIP/RING event and decrements at a reg-
ular rate. When a subsequent TIP/RING event occurs, the timer value is compared to the
RMX[3:0] field, and if it exceeds the value in RMX[3:0], the frequency of the ring is too
high, and the ring is invalidated. The difference between RAS[5:0] and RMX[3:0] identifies
the minimum duration between TIP/RING events to qualify as a ring, in binary-coded incre-
ments of 2.0 ms (nominal). A TIP/RING event typically occurs twice per ring tone period.
At 20 Hz, TIP/RING events would occur every 1/(2 x 20 Hz) = 25 ms. To calculate the cor-
rect RMX[3:0] value for a frequency range [f_min, f_max], the following equation should be
used: RMX[3:0] x 2 ms = RAS[5:0] – 2 ms – (1/(2 x f_max)).
D6
RTO[3:0]
R/W
Ring Timeout
1920
80
128
256
D5
m
m
m
s
m
s
s
s
Rev. 1.0
D4
Function
D3
D2
RMX[3:0]
R/W
D1
Si2401
D0
61