Texas Instruments TRF4900, User Manual, Page: 31 / 45

Main Program Screen
3-4
3.2.2 Mode Options
This section allows the user to control various features of the TRF4900. The
following is a brief summary of the four controls.
1) PLL Turns the phase-locked loop on or off.
2) VCO The voltage controlled oscillator (VCO) is always on.
3) Pwr Amp Allows the power amp to be set to off, 20-dB attenuation,
10-dB attenuation, or 0-dB attenuation states.
4) LPT Port Allows the user to change between the LPT1 and the
LPT2 ports of the controlling computer.
3.2.3 Output Parameters
This section allows the user to turn the TRF4900 Enable, TXData, and Mode
control lines on and off. When the mode control line is off, Mode 0 is defaulted.
When the mode control line is on, Mode 1 is defaulted. Mode 0 initializes using
Words A and D; Mode 1 initializes using Words B and C.
Clock Width and Strobe Width allow the clock and strobe pulse widths to be
increased or decreased.
3.2.4 PLL and MM Options
Allows the change of the APLL value (0, 20, 40...140), the NPLL value (256,
512), and the Modulation Mode (FSK).
3.2.5 Help
Gives a brief description of each control box. For example, after clicking the
PLL box in the Mode Options section on the main program screen, the Help
box will read:
Phase-Lock Loop
0: Off
1: On
Valid in Mode 0 or 1.
Most of the other control boxes follow this format. The first line indicates what
portion of the TRF4900 is being controlled. The next two lines indicate the bit
value. If the PLL is off, bit 12 of Words C and D are equal to 0. If it is on, bit 12
is equal to 1. The last line indicates this control works in both Mode 0 and
Mode 1.
Double clicking in the Help box on the main program screen activates the chip
layout screen.