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CS61318

E1 Line Interface Unit

Cirrus Logic 

CS61318

Reading the control/status registers returns their

current status or setting. Control Register 1 (0x10))

outputs the status of NLOOP and LOS. Additional-

ly, 5, 6, and 7 encoded as shown in Tables 3.

2.12 Interrupts

An interrupt will occur (INT pulls low) in response

to a change in the LOS, AIS or NLOOP bits. The

interrupt is cleared when the host processor writes

a “1” to the respective bit in the control register.

Writing a “1” to LOS or NLOOP over the serial in-

terface has three effects:

1) The current interrupt on the serial interface

will be cleared. (Note that simply reading the

register bits will not clear the interrupt).

2) Output data bits 5, 6 and 7 will be reset as ap-

propriate.

3) Interrupts for the corresponding LOS and

NLOOP will be prevented from occurring.

Writing a “0” to either LOS or NLOOP enables the

corresponding interrupt for LOS and NLOOP.

Bits

765

Status Mode

0 0 0 Reset has occurred, or no program input

0 0 1 RLOOP active

0 1 0 LLOOP active

0 1 1 LOS has changed state since last Clear

LOS occurred

1 0 0 TAOS active

1 0 1 NLOOP has changed state since last

Clear NLOOP occurred

1 1 0 TAOS and LLOOP active

1 1 1 LOS and NLOOP have both changed

state since last Clear NLOOP and Clear

LOS

Table 3. Control Register 1 (0x10) Decoding

2.13 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 CS61318 is reset by simul-

taneously setting RLOOP and LLOOP high for at

least 200 ns. Hardware reset will clear Network

Loopback functionality

2.14 Power Supply

The device operates from a single +5 Volt supply.

Separate pins for transmit and receive supplies pro-

vide internal isolation. These pins should be decou-

DS441PP2

15

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