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EZ-USB Development Kit Manual - Getting Started

Page -16 EZ-USB Development Kit Manual - Getting Started Rev 1.0

The low address byte is “don’t care”. This means you can very efficiently add software test points

using the following code:

This code example uses the 8051 8-bit indirect addressing mode. The MPAGE register (SFR

0x92) supplies the high address byte, and r0 supplies the low address byte. Register r0 does not

require initialization since the low address byte is “don’t care” for the LED decoding.

To turn the LEDS on and off using C code, declare the external memory locations, and then read

their values into dummy variables:

Note: Program execution at these addresses will NOT activate the LEDs.

Indicator Turn ON by reading Turn OFF by reading

D2 0x88-- 0x80--

D3 0x98-- 0x90--

D4 0xA8-- 0xA0--

D5 0xB8-- 0xB0--

D5ON: mov MPAGE,#B8h ; turn D5 on

movx a,@r0 ; dummy read

;

D5OFF: mov MPAGE,#B0h ; turn D5 off

movx a,@r0 ; dummy read

xdata volatile unsigned char D5ON _at_ 0xB800;

xdata volatile unsigned char D5OFF _at_ 0xB000;

unsigned char dum;

dum = D5ON; // turn D5 on

dum = D5OFF; // turn D5 off

D5 D4

These 4 jumpers must be in place

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