CS61581 datasheet(25/37 Pages) CIRRUS

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CS61581

DS211PP8

27 mV/LSB. All voltages are peak voltages across

the TTIP and TRING outputs.

On the secondary of a 1:2 step-up transformer, the

mV/LSB is twice the values stated above. Note that

although the full scale digital input is 3F, it is rec-

ommended that full scale output voltage on the

transformer primary be limited to 2.4 V peak. At

higher output voltages, the driver may not drive the

requested output voltage.

Writing the arbitrary waveform RAM requires a

deviation from normal serial port access. Register

0x13 is the RAM address register for the arbitrary

waveform. Two consecutive address bytes are writ-

ten; first the Address/Command Byte is written to

address 0x13, followed by the address in RAM to

be written. This dual address is then followed by

the data byte for the waveform amplitude. There

are 42 RAM byte locations (numbered 0x00 to

0x29). Each phase amplitude is written as an eight-

bit byte, where the first phase of the symbol is writ-

ten first. The amplitude bytes are written LSB first.

Reading the Arbitrary Waveform RAM follows the

same sequence as the write, except the third mem-

ory access in the sequence is a read instead of a

write.

4.1

Power On Reset / Reset

Upon power-up, the IC is held in a static state until

the supply crosses a threshold of approximately

3 Volts. When this threshold is crossed, the device

will delay for about 10 ms to allow the power sup-

ply to reach operating voltage. After this delay, cal-

ibration of the transmit and receive sections

commences. Because power up conditions can vary

considerably, it is recommended that the device be

reset after the power supply has stabilized to ensure

a known initial operational condition.

The internal frequency generators can be calibrated

only if a reference clock is present. The reference

clock for the transmitter is provided by TCLK. The

reference for the receiver is either the crystal oscil-

lator or MCLK. If both the oscillator and MCLK

are active, MCLK will be used as the reference

source. The initial calibration should take less than

20 ms after pulses are input to the receiver.

In operation, the device is continuously calibrated,

making the performance of the device independent

of power supply or temperature variations. The

continuous calibration function forgoes any re-

quirement to reset the line interface when in opera-

tion. However, a reset function is available which

will reinitiate calibration and clear all registers and

clear the Network Loopback function.

In Host Mode, a reset is initiated by simultaneously

writing RLOOP and LLOOP to the register. The re-

set will set all registers to “0” and initiate a calibra-

tion. A reset will also set LOS high in the Short

Haul configuration.

In Hardware Mode, the CS61581 is reset by simul-

taneously setting RLOOP and LLOOP high for at

least 200 ns. Hardware reset will clear Network

Loopback functionality

Figure 14. Example of Summing of Waveforms

CS61581

DS211F1

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