Si2401
58
Preliminary Rev. 0.9
Reset settings = 0001_1001 (0x19)
SED (RVCZ). Ring Validation Control 2
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name
RAS[5:0]
Type
R/W
Bit
Name
Function
7:6
Reserved
Read returns zero.
5:0
RAS[5:0]
Ring Assertion Time.
These bits set the minimum 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. If a second or subsequent TIP/RING event occurs after the timer has timed out,
the frequency of the ring is too low, and the ring is invalidated. The difference between
RAS[5:0] and RMX[5:0] identifies the minimum duration between TIP/RING events to qual-
ify as a ring, in binary-coded increments 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 correct RAS[5:0] value for a frequency range
[f_min, f_max], the following equation should be used: RAS[5:0] = 1 / (2 x f_min).
