CMX608 datasheet(49/70 Pages) CMLMICRO

49 / 70 page

RALCWI Vocoder

CMX608/CMX618/CMX638

 2014 CML Microsystems Plc

D/608_18_38/11

CLOCK register address $1D

Clock Value

This write only register, together with the DTMFATTEN register ($0A), controls the speed of the

Vocoder's internal processor. This register has no default value and therefore must be set up after

the device is reset. Two speeds can be selected: slow and fast.

Writing $0005 to this register, followed by a write to the DTMFATTEN register, will select the slow

speed. This is the speed at which the internal processor starts up and is suitable for use with

CMX608, CMX618 and CMX638 (only when operated in a half-duplex mode). The fast speed may

also be selected: this will reduce the latency by approximately 3ms but will increase the current

consumption.

Writing $0006 to this register, followed by a write to the DTMFATTEN register, will select the fast

speed. This is the speed which must be selected when operating the CMX638 as a full-duplex

Vocoder.

After writing to the DTMFATTEN register, the host must wait until bit 14 (SVC) of the STATUS

DTMFATTEN register description.

To ensure correct device operation, no other values should be written to this register. The function

of this register should not be confused with 'clock throttling', which is controlled by the THROTTLE

bit (b4) in the POWERSAVE register ($09). Please note that 'clock throttling' is not available in the

CMX638 when used in full-duplex mode.

VDWHLWM register address $1E

Watermark

This write-only register controls the behaviour of the Vocoder-Data-Wanted (VDW) notification by

setting either the high, or low, watermark values. After this register has been written, the host

should wait until bit 15 (RDY) is set in the STATUS register ($40). If interrupts are enabled for this

bit, IRQN will also go low.

No other C-BUS registers should be read or written whilst this

command is in progress.

The device has an audio sample buffer which feeds the digital to analogue converter. Each time a

Vocoder frame is supplied to the device, the complete frame is decoded and the resultant audio

samples are placed in this buffer. The buffer is large enough to accommodate up to 800 samples.

This is the equivalent of 5 x 20ms Vocoder frames.

The device will notify the host that Vocoder data is wanted when the number of samples in the

sample buffer is less than the low watermark value by setting bit 8 (VDW) in the STATUS register

($40).

If interrupts are enabled for this bit, IRQN will also go low.

Once notified, no other

notification will occur until the number of samples in the sample buffer is greater than or equal to

the high watermark.

If notification of Vocoder-Data-Wanted is required, these two watermark values must be explicitly

set after a device reset. There are no defaults for these values. See also section 6.7.

Bits 0 to 10

This value sets the number of samples for either low or high watermark.

Watermark

Bits 11 to 14

These bits are reserved and should be cleared to '0' for correct device operation.

CMX608 数据表(PDF) 49 Page - CML Microcircuits

CMX608 数据表(HTML) 49 Page - CML Microcircuits

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