EV9900A Datasheet, PDF(8/27 Page) CML Microcircuits – Test Access for Important Signals

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

EV9900A Datasheet, PDF (8/27 Pages) CML Microcircuits – Test Access for Important Signals

◁

Evaluation Kit for CMX990

EV9900A

Transmit Mode

The following example âCâ code shows a configuration for the CMX990 transmitter.

register_write(POWER_UP_2, 0x08); //Reset

register_write(POWER_UP_2, 0x01); //Vbias on

register_write(POWER_UP_1, 0xE0); //Clock, BB, Vreg:on & Opamps+Tx+Rx:off

register_write(COMMAND, RESET); //give modem reset command

register_write(CONTROL, 0x00);

register_write(MODE, 0xB1);

//IRQ, Tx Mode, Scrambler & Main DAC enabled

The user should also ensure that the synthesisers are set to appropriate frequencies and

enabled. The transmitter is now ready to start transmission but the offset loop is unlikely to lock

without modulation being generated. To achieve lock, write task TSO (Transmit Scrambler

Output), which will result in a continuous sequence of random data being generated by the

baseband modem. The transmitter is enabled by setting the TxIFRF bit in POWER_UP_1

register_write(COMMAND, TSO);

//Transmit Scrambler Output

register_write(POWER_UP_1,0xE1); //Clock, BB, Vreg, Opamps off , Tx RFIF on

The above sequence just enables the transmitter. The power amplifier can now be enabled using

the DAC0 Output. This DAC has an automatic ramping circuit to allow an accurate power

ramping profile to be applied to the power amplifier.

register_write(AUX_DAC_0_MSB,0x39);

lock

//Turn PA on at minimum power to all

For some operating frequencies the free-running frequency of the Tx VCO needs to be within

certain limits of the desired Tx frequency (as described in the datasheet). On the EV9900A this

can be achieved using the pre-charge facility as follows:

Register_write(0x24,0x11);

Delay(1000);

Register_write(0x24,0x01);

//Enable Tx VCO Charge

//Wait while VCO tunes

//Disable Tx VCO Charge

The power amplifier may now be either ramped up or, for basic testing, enabled to the required

power. An output power of ~1W is generally achieved with a DAC0 value of 0xb0.

register_write(AUX_DAC_0_MSB,0xb0);

//PA output approx 1W

UM9900A/3

▷