Peripheral ATMega103 Port Direction Connection External SRAM A[0-7] In/Out Address/Data C[0-7] Out Upper Address 24x2 LCD D[0] Out RS, Pin 4 D[1] Out RD, Pin 5 D[2] Out EN, Pin 6 D[4-7] In/Out D0-4, Pins 11-14 push-buttons F[0] In Volume decrease button F[1] In Volume increase button F[2] In Previous track button F[3] In Next track button STA013 MP3 Decoder B[0] Out Reset, Pin 26 (shared) B[2] Out SDI, Pin 5 B[3] In/Out SDA, Pin 3 B[4] Out SCL, Pin 4 B[5] Out SCKL, Pin 6 F[6] In DATA_REQ, Pin 28 CD-ROM ATA Interface A[0-7] In/Out lower 8 bits of bus, Wires 4,6,8,10,12,14,16,18 B[0] Out Reset, Wire 0 (shared) B[6] Out DIOR, Wire 25 C[0-2] Out DA0-2, Wires 35,33,36 C[3] Out CS1FX, Wire 37 C[4] Out CS3FX, Wire 38 E[0-7] In/Out upper 8 bits of bus, Wires 3,5,7,9,11,13,15,17