ST75C540 datasheet(47/84 Pages) STMICROELECTRONICS

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VIII.2.4 - Quality Status

The quality bytes STAQUAand STAQUAS monitor an evaluationof the line quality. They are updated once

per baud and their value ranges from 127 (perfect quality) to 0 (terrible quality). This value is automaticaly

adjusted according to the current receiving mode. Refer to the following chart to convert the value of

STAQUA into its Bit Error Rate equivalence. The time constant for STAQUA is 100ms. The slow quality

byte (available on STAOP1 in Fax and Data mode except FSK) STAQUAS gives the equivalent quality with

a 1 seconde time constant.

VIII - STATUS DESCRIPTION (continued)

-3

-4

-5

-6

-7

-8

-9

127

STAQUA

BER

-2

VIII.2.5 - Optional Status

According to the operating mode of the ST75C530/540 the optional status is displaying different informa-

tions.

The optional status are automatically reprogrammed after each CONF command with the address of the

variablesto monitor according with the operating mode selected (CONF_OPER). After the CONF command

the user must overwrite this default programming by using the DOSR command. In order to change the

default set-up please refer to the “RAM Mapping application note” (delivered on request according to

revision number) to obtain the addresses of the DSP Internal variables.

VIII.2.5.1 - Default Optional Status in All modes Except MODEM

While in Tone mode the format of the STAOP word is as follows :

Optional Status Words

Add.

Name

Bit

543

$0C

STAOP0

TDT7

TDT6

TDT5

TDT4

TDT3

TDT2

TDT1

TDT0

$0D

STAOP1

TDT15

TDT14

TDT13

TDT12

TDT11

TDT10

TDT9

TDT8

$0E

STAOP2

RING_PERIOD

(1)

$0F

STAOP3

TDT19

TDT18

TDT17

TDT16

DTMF_DIGIT

(4)

Notes : 1. RING_PERIOD is valid when the Bit 3 of the STATUS0 (STA_RING goes high. This value is updated at eac h falling edge of the

RING Signal. The RING_PERIOD value must be multiplied by 2400 to obtain the Period in second.

2. TDTx (x in [0..15]) is the Output of the 16 Tone detectors x (sampling rate 7200Hz).

3. TDTy (y in [16..19] is the Output of the secondary Tone detectors (sampling rate 4800Hz or 9600Hz) with absolute comparison

or relative comparison.

4. DTMF_DIGIT is valid when the Bit 7 of STATUS1 (STA_DTMF) goes high. This value remains unchanged until a new DTMF

Digit is detected.

ST75C530 - ST75C540

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