TMS320F241_13 Datasheet, PDF (53/122 Pages) Texas Instruments – DSP CONTROLLERS

TMS320F243, TMS320F241
DSP CONTROLLERS
SPRS064D − DECEMBER 1997 − REVISED FEBRUARY 2006
analog-to-digital converter (ADC) module
A simplified functional block diagram of the ADC module is shown in Figure 11. The ADC module consists of
a 10-bit ADC with a built-in sample-and-hold (S/ H) circuit. A total of 8 analog input channels is available on the
F243/F241. Eight analog inputs are provided by way of an 8-to-1 analog multiplexer. Maximum total conversion
time for each ADC unit is 1 µs. Reference voltage for the ADC module is 0−5 V and is supplied externally.
Functions of the ADC module include:
D The ADC unit can perform single or continuous S / H and conversion operations. When in continuous
conversion mode, the ADC generates two results every 1700 ns (with a 20-MHz clock and a prescale factor
of 1). These two results can be two separate analog inputs.
D Two 2-level-deep FIFO result registers
D Conversion can be started by software, an external signal transition on a device pin (ADCSOC), or by
certain event manager events.
D The ADC control register is double-buffered (with a shadow register) and can be written to at any time. A
new conversion can start either immediately or when the previous conversion process is completed.
D In single-conversion mode, at the end of each conversion, an interrupt flag is set and the peripheral interrupt
request (PIRQ) is generated if it is unmasked/enabled.
D The result of previous conversions stored in data registers will be lost when a third result is stored in the
2-level-deep data FIFO.
A/D overview
The “pseudo” dual ADC is based around a 10-bit string/capacitor converter with the switched capacitor string
providing an inherent S/ H function. (Note: There is only one converter with only one inherent S/H circuit.) This
peripheral behaves as though there are two analog converters, ADC #1 and ADC #2, but in fact, it uses only
one converter. This feature makes the A/D software compatible with the C240’s A/D and also allows two values
(e.g., voltage and current) to be converted almost simultaneoulsy with one conversion request. V_CCA and V_SSA
pins must be connected to 5 V and analog ground, respectively. Standard isolation techniques must be used
while applying power to the ADC module.
The ADC module, shown in Figure 11, has the following features:
D Up to 8 analog inputs, ADCIN00−ADCIN07. The results from converting the inputs ADCIN00−ADCIN07 are
placed in one of the ADCFIFO results registers (see Table 16). The digital value of the input analog voltage
is derived by:
Digital Value + 1023
Input Analog Voltage * V_REFLO
V_REFHI * V_REFLO
D Almost simultaneous measurement of two analog inputs, 1700 ns apart
D Single conversion and continuous conversion modes
D Conversion can be started by software, an internal event, and/or an external event.
D V_REFHI and V_REFLO (high- and low-voltage) reference inputs
D Two-level-deep digital result registers that contain the digital vaules of completed conversions
D Two programmable ADC module control registers (see Table 16)
D Programmable clock prescaler
D Interrupt or polled operation
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