RCVDL56DPFL/SP, RCV56DPFL/SP, and RCV336DPFL/SP Designer’s Guide
12-6
1119
The gain may also be altered through address B7Eh. This location is reset to default after a RREN and is adjustable only
when the modems are connected. The total input gain should not bring the input signal level above -16 dBm to avoid input
saturation. The following table illustrates the relative gain in 2 dB steps:
Microphone Relative Gain (dB)
Value in B7E (Hex)
+10
1500
+8
1200
+6
0F00
+4
0C00
+2
0A00
0
0800 (default value)
-2
0500
-4
0200
-6
FF00
-8
FD00
-10
FA00
The equation to calculate the relative gain change for both mic and speaker is as follows:
Gain change in dB = 20Log(M#2) - 20Log(M#1)
Where:
M = 2(x + y/2048)
The 16-bit signed value is broken down as: xxxxxyyyyyyyyyyy (y = bits 0-A and x = bits B-F)
M#1 is calculated based on the current gain value.
M#2 is calculated based on the new gain value.
12.1.11 TELIN/TELOUT Gain Control
When using TELIN/TELOUT for handset operation, the gain control has to be through address B7Eh for TELIN and address
990h for TELOUT. The VOLUME bits and mic gain control at address 3D3h do not apply.
12.1.12 Handset Echo Canceller
When bit 400h:5 is set for handset operation, the handset echo canceller must be enabled to avoid echoes on the remote
end. To enable the echo canceller, write 8004h to address A5Ch. If read back, a value of 0004 or 4004h will be present.
8004h should be written to A5C once the modems are connected and handset operation is desired.
The half-duplex gain control bit (400h:7) should also be set to further suppress the echo. When bit 400h:5 is reset for
headset or mic/spkr operation, disable the echo canceller by writing 0000 to A5Ch.
Summary of Contents for RC336DPFL
Page 193: ...INSIDE BACK COVER NOTES ...