Silicon Laboratories SI2493/57/34/15/04, SI2494/39 manual Si3000 Configuration

AN93

7.3. Si3000 Configuration

7.3.1. Microphone and Speaker Ports

The TAM and Speakerphone applications use two sets of microphones and speakers: one for the handset and one for hands-free operation. For the Si24xxVMB REV 2.0, the handset circuit uses the MIC input and SPKR_L output. The Si24xxVMB REV 2.0 allows configuration of the MIC, SPKR_L, and matching ground signals on any handset pinout. There is no industry standard for handset pinout. For the Si24xx-VMB REV 2.0, the speakerphone/hands- free TAM circuit uses the LINEI input and the LINEO output. The LINEO is sent to an external amplifier.

7.3.2. Register Settings

Figure 30 illustrates the register bit fields and corresponding values used to control the gain/attenuation, filtering, output drivers, and signal selection. From the software driver perspective, the Si3000 has three configuration groups that are applied for the given system states: handset, speakerphone, and hands-free TAM. For applications requiring handset recording of the OGM, the software may use a fourth configuration for handset TAM. These configuration groups define the digital gains, analog gains, and control bit settings for registers 1, 5, 6, 7, and 9 of the Si3000. Speakerphone algorithm includes input and reference gains that require a lower gain in the Si3000. For Hands-Free TAM, the speakerphone voice path is disabled, so a higher analog gain can be used.

7.3.3. System Voice Modes

A system voice mode consists of the Si24xx ISOmodem and Si3000 settings combined with the PSTN status to achieve a desired function. These modes describe the status of the hook switch, the modem voice path, Si3000 configuration (input, output, and gains), and the allowed operations. Figure 31 illustrates the transition events among these modes.

7.3.3.1. TAM Hands-Free

This is the general idle mode for recording an OGM/local message (+VRX) and reviewing an ICM/local message (+VTX). All detectors are functional and incoming rings are indicated on the speaker via a tone or a melody. The modem is on-hook routing audio between the Si3000 and the DTE interface. The modem voice path is configured for half-duplex audio with speakerphone algorithm disabled. The Si3000 audio transmit and receive path is muted/ unmuted to allow half-duplex control for proper TAM operations. Side tone is disabled. Handset TX/RX coefficients are applied. The Si3000 is using the LINEI and LINEO signals with hands-free TAM gain settings.

7.3.3.2. TAM Handset

This is variation to the TAM Hands-Free mode above, with the exception that the handset is used to review a locally-recorded message or ICM privately. The Si3000 is using the MIC and SPKRR and/or SPKRL signals with handset gain settings. A raised handset usually triggers off-hook transition, so the controller would have to support a special mode to not switch off-hook into Handset mode.

7.3.3.3. Speakerphone

This mode is used to conduct a hands-free voice call. The modem is off-hook and routing audio between Si3000 and DAA. The modem voice path is configured for full-duplex audio with speakerphone algorithm enabled. Side tone is disabled. Speakerphone TX/RX filter coefficients are applied. The Si3000 is using the LINEI and LINEO signals with speakerphone gain settings.

7.3.3.4. Handset

This mode is used to conduct a private voice call. The modem is off-hook and routing audio between the Si3000 and DAA. The modem voice path is configured for full-duplex audio with speakerphone algorithm disabled. Side tone is enabled. Handset TX/RX filter coefficients are applied. The Si3000 is using the MIC and SPKRR and/or SPKRL signals with handset gain settings. This mode is supported by all parts.

192 Rev. 1.3