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MSM7602

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APPENDIX

Differences Between the MSM7602 and the MSM7520/7620

Introduction

The MSM7602 is the improved version of the MSM7520 with improved usage. Thus, there are no

differences in echo canceling characteristics.

Enhancements

• A new clock frequency of 19.2 MHz.

The basic clock frequency of the MSM7520/7620 was 18 or 38 MHz, while the basic clock

frequency of MSM7602 is 19.2 MHz. (MSM7602 can be applied at a frequency of 18 MHz.

However, external SYNC and SCK are required because the periods of SYNCO and SCKO are

varied.)

• Adoption of full-fledged 8-bit data through-mode

In the through-mode for the MSM7520 (HCL pin: "H"), an internally processed PCM signal was

Analog to analog conversion causes no problem since both values are the minimum ones, but

data transfer in the through-mode encounters problems. Hence, in the MSM7620/7602, the

complete data trough-mode has been implemented.

• Control of input timing to control pins (NLP, HCL, ADP, ATT and GC)

In MSM7520, asynchronous changes in a control pin may result in malfunctioning. This

problem stems from the fact that information on control pins is checked several times during

the execution of a program over one cycle and the state of a control pin is changed between the

first and second half periods.

The MSM7620/7602 provides an internal circuit for using an INT signal to hold control pin

information for one cycle. Thus, external timing control is not needed.

The howling detector control pin (HD) is added.

The MSM7602 can prevent the false detection of the howling detecter cause by tone signals by

providing the howling detecter control pins.

• Introduction of 256 kHz internal clock output (SCKO) for PCM transmission

Internal sync signals (SYNCO and SCKO) in MSM7520/7620 are rated at 8 kHz and 200 kHz,

respectively. At a frequency of 8 kHz, PCM multiplexing can be applied to no more than three

channels.

In the MSM7602, SCKO is rated at 256 kHz, while SYNCO at 8 kHz. Thus, PCM multiplexing

can be applied with up to four channels.

• Addition of basic clock output

The use of a crystal oscillator for a clock in the MSM7520/7620 requires an oscillating circuit

installed in each of two or more cascade-connected IC chips.

Since the MSM7602 supports basic clock output, only one IC chip requires an oscillating circuit.

(The MSM7602-001TS-K does not provide the basic clock output.)