Texas Instruments MSC1210 manual Tone Generator, ToneFrequency +1

Models: MSC1210

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Tone Generator

The three bits that together make up TPCNTL, control the function of the PWM/ tone generator. The function of the generator is determined according to the table above.

TPCNTL.0 enables or disables the PWM/tone generator. If set to ‘1’, the block will act as either a PWM or tone generator depending on the setting of TPCNTL.1. When TPCNTL.0 is ‘0’, the function block is completely disabled. This state of the block is the default state.

When TPCNTL.1 is 0, the block acts as a pulse width modulator in which a modulated pulse is generated whose duty cycle is determined by the PWM Duty and PWM Period registers. The range of frequencies that can be generated is 4kHz to 500kHz with a 1MHz clock, or up to 16MHz with sysclock.

When TPCNTL.1 is 1, the block acts as a tone generator which may generate either a staircase or square waveform, depending on further configuration. In either case, the frequency range is 60Hz to 16MHz.

11.2 Tone Generator

When TPCNTL [1:0] = 11, the block functions as a tone generator with either a square or staircase waveform that has two or three levels of 0V, high impedance, and VDD volts, respectively. The widths of each step in the staircase waveform are chosen so that the error between the staircase waveform and a sinusoidal waveform of the same frequency is minimized; in staircase mode, the output is high impedance for the last 1/4 of each half period.

ToneFrequency +1

2 @ PWMPeriod[15 : 0] @ TBASE

Where:

TBASE = TCLK when SPDSEL = 1

TBASE = TUSEC when SPDSEL = 0.

The TONE/PWM output pin is fed to a circuit depending upon the application. In the Figure 11−2, the circuit of a tone generator is shown. When the output is high-impedance, the voltage value that is buffered and fed to the speaker is VDD/2.

Figure 11−2. Tone Generator Circuit

Pulse Width Modulator/Tone Generator

11-3

 

Page 127
Image 127
Texas Instruments MSC1210 manual Tone Generator, ToneFrequency +1