Motorola MCU 68HC912 Bedienungsanleitung PDF herunterladen (Seite 4)

SLAA108A

4 SPI-Based Data Acquisition/Monitor Using the TLC2551 Serial ADC

TLC2551 Serial Interface

The TLC2551 is a 12-bit serial output successive approximation analog to digital converter. The

device is available in 8-pin MSOP and SOIC packages. Since there are no configuration

registers in the device, it is relatively simple to use. Table 1 lists the I/O pins and their function.

Table 1. I/O Pins of the TLC2551

Pin Description

/CS Chip select – An active low signal. A high-to-low transition removes the SDO pin from 3-state.

REF

External reference input

GND Ground return for internal circuitry

AIN Analog input

SCLK Input serial clock

Positive supply voltage (5VDC)

FS Frame sync

SDO 3-state serial output for the conversion result.

TLC2551 Timing

Figure 3. TLC2551 Timing Diagram

The TLC2551 requires 12 SCLK’s to complete its sampling. The sampling period begins after

the fourth falling SCLK edge. Chip select must be held in a low state for the entire 16 clock

cycles before a valid conversion will take place. When operated with an SPI controller, the chip

select signal can be removed after two 8-bit transfers from the SPI port.

The conversion cycles starts after the 16

falling SCLK edge and takes 28 clock cycles to

complete. The results are presented on SDO during the next cycle.

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Motorola MCU 68HC912 Bedienungsanleitung Seite 4