CS61310

DS440F1 FEB ‘03

15

LOOPUP

Loop Up

Setting LOOPUP to “1” causes the data pattern 00001... to be repetitively transmitted.

RPWDN

Receiver Power Down

When RPWDN = 1, the receiver circuitry is powered down, but the transmitter is still active.

TxHIZ

Transmitter High Impedance

When TxHIZ = 1 the transmitter goes to a low-power, high-impedance state

RSVD

Reserved. Set to 0 for proper operation.

2.15

Equalizer Gain (EQGAIN): Address 0x12

EQ[4:0]

The receive equalizer gain settings are broken down into 20 segments and provided at the five

LSBs of this register, EQ4 - EQ0. 00001 corresponds to -2 dB, 10100 corresponds to -40 dB.

The three MSBs are don’t cares.

2.16

RAM Address (RAM): Address 0x13

RAM[7:0]

The RAM address pointer for the arbitrary waveform memory;

a special write procedure must be followed to write the waveform RAM.

2.17

Interrupts

An interrupt will occur (INT pulls low) in response

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

terrupt 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.

Reading the registers returns their current status or

setting. Register 16 outputs the status NLOOP and

LOS and has bits 5, 6, and 7 encoded as shown in

Table 4.

Writing the arbitrary waveform RAM requires a de-

viation from normal serial port access. Register 19

is the RAM address register for the arbitrary wave-

form. Two consecutive address bytes are written;

first the Address/Command Byte is written to ad-

dress 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 h00 to h29).

7 (MSB)

6543

21

0 (LSB)

X

X

X

EQ4

EQ3

EQ2

EQ1

EQ0

7 (MSB)

6543

21

0 (LSB)

RAM.7

RAM.6

RAM.5

RAM.4

RAM.3

RAM.2

RAM.1

RAM.0

Table4. Register16 Decoding

Bits

Status

765

0

0

0 Reset has occurred, or no program input

001 RLOOP active

0

1

0 LLOOP active

0

1

1 LOS has changed state since last Clear

LOS occurred

100 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