/* * bl_board_init.c * * Created on: 19.08.2008 * Author: heiko, kaspar */ #include "cpu.h" #include "bits.h" #include "VIC.h" #define PLOCK 0x400 static void feed(void) { PLL0FEED = 0xAA; PLL0FEED = 0x55; } void bl_init_clks(void) { // Setting the Phased Lock Loop (PLL) // ---------------------------------- // // Olimex LPC-P2148 has a 12.0000 mhz crystal // // We'd like the LPC2148 to run at 60 mhz (has to be an even multiple of crystal) // // According to the Philips LPC2148 manual: M = cclk / Fosc where: M = PLL multiplier (bits 0-4 of PLLCFG) // cclk = 60000000 hz // Fosc = 12000000 hz // // Solving: M = 60000000 / 12000000 = 5 // // Note: M - 1 must be entered into bits 0-4 of PLLCFG (assign 4 to these bits) // // // The Current Controlled Oscilator (CCO) must operate in the range 156 mhz to 320 mhz // // According to the Philips LPC2148 manual: Fcco = cclk * 2 * P where: Fcco = CCO frequency // cclk = 60000000 hz // P = PLL divisor (bits 5-6 of PLLCFG) // // Solving: Fcco = 60000000 * 2 * P // P = 2 (trial value) // Fcco = 60000000 * 2 * 2 // Fcc0 = 240000000 hz (good choice for P since it's within the 156 mhz to 320 mhz range) // // From Table 22 (page 34) of Philips LPC2148 manual P = 2, PLLCFG bits 5-6 = 1 (assign 1 to these bits) // // Finally: PLLCFG = 0 01 00100 = 0x24 // // Final note: to load PLLCFG register, we must use the 0xAA followed 0x55 write sequence to the PLLFEED register // this is done in the short function feed() below // // Setting Multiplier and Divider values PLL0CFG = 0x24; feed(); // Enabling the PLL */ PLL0CON = 0x1; feed(); // Wait for the PLL to lock to set frequency while(!(PLL0STAT & PLOCK)) ; // Connect the PLL as the clock source PLL0CON = 0x3; feed(); // Enabling MAM and setting number of clocks used for Flash memory fetch MAMTIM = 0x3; MAMCR = 0x2; // Setting peripheral Clock (pclk) to 1/2 System Clock (cclk) VPBDIV = PCLK_DIV; } void bl_init_ports(void) { }