ST75C520 datasheet(29/45 Pages) STMICROELECTRONICS

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Starting at the adddress $08 the status area have the following format :

Add.

Name

Bit

5432

$08

SYSERR

ERR_RTK

ERR_IPRM ERR_IOCD

ERR_RX

ERR_TX

$09

STATUS0

STA_109F STA_CPT10 STA_CPT1 STA_CPT0 STA_RING

STA_106

STA_107

STA_109

$0A

STATUS1

STA_DTMF STA_FLAG

STA_HR

STA_AT

STA_CCITT

STA_H

$0B

STAQUA

Quality

$0C

STAOP0

Depend on operating mode (see below)

$0D

STAOP1

$0E

STAOP2

VII.2.2 - Error Status

The error status changes each time an error occurs. When the ST75C520 signals an error by setting one

of the SYSERR bit, it generates an interrupt IT0. These bits can only be cleared by the host controler using

the CSE command.

The meaning of the different bits of the SYSERR byte is discribed below :

SYSERR

Field

Pos.

Meaning when set

ERR_TX

Transmit buffer underflow. Loss of synchronisation between the host and ST75C520

transmit data buffer managment.

ERR_RX

Receive buffer overflow. Loss of synchronisation between the host and ST75C520 receive

data buffer managment.

ERR_IOCD

Incorrect CCI command

ERR_IPRM

Incorrect parameter for the CCI command

ERR_RTK

Real time kernel error. ST75C520 not able to perform all its tasks within the baud period

(transmit or receive samples lost).

VII.2.3 - Modem General Status

The modem general status word is composed of two bytes STATUS[0] and STATUS[1]. Any bit change can

generate an IT4 interrupt. Using the DSIT command allows the selection of the corresponding bit that will

generate an interrupt each time they will change. The default pattern is $3F for STATUS[0] and $FF for

STATUS[1].

The different bits have the following meaning :

STATUS[0]

Field

Pos.

Meaning when set

STA_109

CCITT circuit 109 (carrier detect). Indicates that valid data are received. When 0 the output

data RxD are clamped to constant mark. Valid only in modem mode.

STA_107

CCITT circuit 107 (data set ready). Valid only in modem mode.

STA_106

CCITT circuit 106 (clear to send). Indicates that the training sequence has been completed

and that any data at TxD pin (serial mode) or in the transmit buffer (parallel mode) will be

transmitted. valid only in modem mode.

STA_RING

Ring detected. A ring signal (from 15Hz to 68Hz) is present at the RING pin. Valid only in

tones modes. The precise frequency can be read in the optional status byte STAOP2. The

detection time is 1 period of the ring signal. The detection lost time in 20ms after the last

transition on the ring signal.

STA_CPT0

Call progress tone detector #0. Low pass filter 650Hz. Valid only in tones modes.

STA_CPT1

Call progress tone detector #1. High pass filter 600Hz. Valid only in tones modes.

STA_CPT10

Signal in filter #0 is highter than #1. Valid only in tones modes.

STA_109F

Fast Carrier Detect. Valid only in modem mode.

ST75C520

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