Hi. I have this simple code that defines some constants in code: #include <REG922.H> code const unsigned char LEDRegister0[] = {0xff,0xfe,0xfd,0xfb,0xff,0xff,0xff,0xff,0xf7,0xff,0xff,0xbf}; code const unsigned char LEDRegister1[] = {0x7f,0xff,0xff,0xff,0xef,0xfd,0xfb,0xf7,0xff,0xbf,0xfe,0xff}; code const unsigned char Pattern1[] = {54,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,19,21,25,27,30,33,36,40,45,50,50,45,40,36,33,30,27,25,21,19,19,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; code const unsigned char Pattern2[] = {54,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,19,21,25,27,30,33,36,40,45,50,50,45,40,36,33,30,27,25,21,19,19,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; code const unsigned char Pattern3[] = {54,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,19,21,25,27,30,33,36,40,45,50,50,45,40,36,33,30,27,25,21,19,19,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; void main() { unsigned char i; P1M1 = 0; for(;;) { P1 = 0xaa; P1 = 0x55; } } When I simulate this code it runs fine, but when I download it to my chip (an LPC920), it doesn't run. I then remove the last constant definition named Pattern3, recompile and now the code simulates AND runs in the chip. I started from the Blinky example and simply changed the target chip to compile. I'm using small memory model and small code size (2k or less). If anyone can tell me what I'm doing wrong, I would be grateful. Thanks, Marc.