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TLC2543 TO TMS370 Microcontroller Interface

Microcontroller Features

Within the family of TMS370 microcontrollers there are several versions which contain a serial peripheral interface

(SPI) facility. One of these versions should be chosen to implement the interface method described below. One such

version is the TMS370C010 which is used to illustrate the method.

Interface Circuit

Figure 9 shows the circuit interconnections for the TLC2543 to TMS370C010 microcontroller interface. Note that no

extra logic is required to implement this interface.

Analog

Inputs

AIN0

AIN1

AIN2

AIN3

AIN4

AIN5

AIN6

AIN7

AIN8

AIN9

AIN10

I/O CLOCK

DATA INPUT

DATA OUT

TLC2543

5 V

SPICLK

SPISIMO

SPISOMI

5 V

TMS370

5 V

8 × SPST

Switch

8 × 10 kΩ

Figure 9. TLC2543 to TMS370C010 Interface Circuit

Depending upon the layout of the particular printed circuit board used it may be necessary to insert a small value

capacitor of between 50 and 100 pF between the I/O CLOCK input of the TLC2543 and ground. This has the effect of

ensuring that data applied to the DATA INPUT terminal of the TLC2543 is valid before the positive going transition

of the I/O CLOCK.

The positive reference, REF+, to the TLC2543 is provided directly from the V

CC+

supply.

The four digital interface terminals, I/O CLOCK, DATA INPUT, DATA OUT, and CS, of the TLC2543 connect directly

to the SPICLK, SPISIMO, SPISOMI and D7 terminals respectively of the TMS370C010.

The operation mode and channel number of the TLC2543 is determined by the serial data which is sent to its DATA

INPUT terminal.

Software

List 1 contains the software listing for the program which controls the interface illustrated in Figure 5. The software

consists of the main program and three subroutines called DATA IN, ADC and STORE. DATAIN reads in the channel

select and mode control data into a holding register and maps the channel select number to a corresponding pair of

registers between R64 and R91. The mapping vector is held in register R10. ADC provides the chip select pulse, controls

the SPI operation, and puts the MSByte and LSByte of each conversion result into registers R20 and R21 respectively.

STORE puts the MSByte into the even number register and the LSByte into the odd number register mapped by the

contents of register R10.

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 25 26

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