VII.1.3 - CR Command

Issuing a CR command causes the ST75C520 to dump a specific memory location in complex mode. This

instruction is particularly useful for equalizer state analysis or for software eye-pattern display. The report

area has this meaning :

RP7

RP6

RP5

RP4

RP3

RP2

RP1

RP0

COMREP[0]

IP7

IP6

IP5

IP4

IP3

IP2

IP1

IP0

COMREP[1]

RP0..RP7 is the MSB part of the 16-bit value of the real part and IP0..IP7 is the MSB part of the imaginary

part. The CR command insures that the real and imaginary part of the desired complex value are sampled

internally at the same time. The address given in the parameter field of CR is the address of the real part.

VII.1.4 - MR/TDRC/TDRW/IDT Commands

The report issued by the MR/TDRC/TDRW/IDT commands follow the same rules as for CR. The report

meaning is :

D7

D6

D5

D4

D3

D2

D1

D0

COMREP[0]

D15

D14

D13

D12

D11

D10

D9

D8

COMREP[1]

D0..D15 is the 16-bit value required by the MR/TDRC command.

In the case of IDT, D15..D12 contains the product identification (2 for ST75C520), D11..D8 contains the

hardware revision identification and D7..D0 contains the software revision identification.

VII.2 - Modem Status

VII.2.1 - Modem Status Description

The Status of ST75C520 is divided into 4 fields :

- The error status byte SYSERR that provides information about error. This status can trigger an IT0

interrupt,

- The general status byte STATUS[0] and STATUS[1] that contains all the modem signals. These status

bytes can trigger an IT4 interrupt,

- The quality status STAQUA, that contains the quality of the received transmission,

- The optional status bytes STAOP[0], STAOP[1] and STAOP[2], that contains additional information

regarding the ST75C520 operatingmode. This default information can be changed to monitor any internal

variables using the DOSR command.

All these informations are updated on a Baud basis :

Mode

Baud Rate

CLK (Hz)

Tone, DTMF, Voice

2400

9600

Bell 103 (full duplex)

2400

9600

V.21 (full duplex)

2400

9600

V.23 (full duplex)

2400

9600

V.27ter 2400bps

1200

2400

V.27ter 4800bps

1600

(1)

4800

V.29

2400

9600/7200/4800

V.17

2400

14400/12000/9600/7200

V.33

2400

14400/12000

V.21 channel 2

2400

300

Notes : 1. The tone detectors outputs are update 800 times by second.

2. This baud rate defines also, the maximum command rate. Each baud time the ST75C520 looks at the COMSYS location

(addesss $00) to see if a command have been sent by the host processor. If the content of this location is different from zero the

ST75C520 execute the command.

ST75C520

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