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4.2.2 Seven-segment display hardware interface

First define macro expressions for the pins which the seven-segment displays are connected to. The

example shown is for the RC200:

static macro expr SevenSeg0Pins = {"L5", "G4", "F3", "K3", "L4", "L3", "H4",

"G3"};

static macro expr SevenSeg1Pins = {"K4", "G5", "H3", "L6", "F5", "H5", "J3",

"J4"};

Now define registers to hold the values to be displayed, initialising them to zero. The example shown is

for the RC200, which has two seven-segment displays, hence the array of two 8-bit unsigned integers.

static unsigned 8 SevenSeg[2] = {0, 0};

Now define a Handel-C interface to attach the pins to the variables. Use the Handel-C

bus_out

interface as the pins are outputs from the device driver.

static interface bus_out () SevenSeg0Out (SevenSeg[0]) with {data =

SevenSeg0Pins};

static interface bus_out () SevenSeg1Out (SevenSeg[1]) with {data =

SevenSeg1Pins};

Note that making the SevenSeg variable and the various macros static prevents them from being

visible outside the file they are defined in.

Now implement a macro procedure to display a ‘shape’ on the seven-segment display. The figure below

shows how the segments of the display are numbered, so that when an 8-bit data value is written to the

display, bit 0 is the top segment, and bit 7 is the decimal point.

macro proc SevenSeg0WriteShape (Shape)

{

SevenSeg[0] = Shape;

}

NUMBERING OF DISPLAY SEGMENTS

Now implement a macro procedure which accepts a 4-bit unsigned integer and displays the

corresponding hexadecimal digit on the seven-segment display. The decimal point is set according to a

further 1-bit unsigned integer parameter. The required shapes to display hexadecimal digits have been

provided in the ROM

TranslationROM0 in the example project (TutorialSevenSeg1).

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