Evaluation Kit for CMX990
EV9900A
Transmit Mode
The following example ‘C’ 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.
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);
//Turn PA on at minimum power to all
lock
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
© 2007 CML Microsystems Plc
8
UM9900A/3
CMLMICRO [ CML MICROCIRCUITS ]
