Evaluation Kit for CMX990
EV9900A
3.3
Operation
The CMX990 is a complex RF and Baseband Modem IC. It is recommended that the user
familiarise themselves with the datasheet of this device prior to attempting to use the EV9900A.
To use the EV9900A the user will need a mechanism to send and receive data and commands
via the 8-bit parallel host µController interface on the CMX990, which is brought out on connector
J13 on the EV9900A. The CMX990 datasheet gives details of the registers and commands. To
operate the CMX990, some typical command sequences are given below:
Data Rate
The default data rate with a 14.4MHz reference is 6000bps. Data rates can be configured using
the clock control register in the CMX990 (C-BUS address $29). The following example C code
shows a typical configuration for common data rates:
register_write(CLOCK_CONTROL, 0x45);
register_write(CLOCK_CONTROL, 0x85);
register_write(CLOCK_CONTROL, 0x46);
//9600 bps e.g. 25kHz channel
//4800 bps e.g. 12.5kHz channel
//8000 bps e.g. 12.5kHz channel
Receive Mode
The following example C code shows a typical configuration for reception.
register_write(POWER_UP_2, 0x08); //Reset
register_write(POWER_UP_2, 0x01); //Vbias on
register_write(POWER_UP_1, 0xEE); //Clock+BB+Vreg,+Rx:on & Opamps+Tx:off
register_write(POWER_UP_2, 0xF1); //DACs on
register_write(AUX_DAC_1_MSB,169); //AFC to mid rail (1.65V)
//Set up synths:
set_main_synth(0x8480,0x807530);
set_aux_synth(0x8090,0x870C);
register_write(CONTROL, 0xE9);
register_write(MODE, 0xD2);
//750MHz, low side, Rx Freq=420.1MHz
//(assuming ref 14.4MHz & comp 12.5kHz)
//180.4MHz (for 45.1MHz IF)
//(assuming ref 14.4MHz & comp100kHz)
//AGC max gain & run, IQ offset fine,
//AFC Slow, PLL Narrow
//IRQ enabled, scrambler enabled,
//INV bit enabled, Main ADC enabled, Rx mode
register_write(POWER_UP_2,0xF5);
register_write(COMMAND, 0x60);
//Turn LNA on.
//Acquire DC offset & AFC
//DelayBy(90000);
//Wait for Offset to complete
Following the above routines the user may initiate reception of data using the modem task
commands in Command register ($01).
© 2007 CML Microsystems Plc
7
UM9900A/3
CMLMICRO [ CML MICROCIRCUITS ]
