C645的PLL的倍频系数无法更改

你好，请问使用官网上的GEL文件无法更改PLL时钟的倍频系数PLLM寄存器的值，我开始改为20后就再也改不了了，为什么？

Shine：

请问您具体是怎么改的？方便把代码帖出来吗？是PLLM寄存器的值改不了？还是改了后，时钟输出不对？

user5910726：

回复 Shine:

PLLM寄存器的值改不了。代码用的官方的GEL文件里的初始化代码：
void init_PLL()
{int i;int PLLM_val =20; int PREDIV_val =3;int PLLDIV4_val = 3;//int PREDIV_val =1;//int PLLDIV4_val = 4;//int PREDIV_val =1;//int PLLDIV4_val = 3;int PLLDIV5_val = 3;
//if (Get_Board_Rev == 0)//PLLM_val = 25; // Old Rev, 40MHz CLKIN x 25 = 1GHz//if (Get_Board_Rev == 1)PLLM_val = 20; // Old Rev, 50MHz CLKIN x 20 = 1GHz//if (Get_Board_Rev >= 2)//PLLM_val = 24; // Old Rev, 50MHz CLKIN x 24 = 1.2GHzif (PLLM_val > 0 && PLLM_val < 32){if ( (PREDIV_val > 0) && (PREDIV_val < 33) ){/* In PLLCTL, write PLLENSRC = 0 (enable PLLEN bit).*/*(int *)PLLCTL_1 &= ~(0x00000020);/* In PLLCTL, write PLLEN = 0 (bypass mode).*/*(int *)PLLCTL_1 &= ~(0x00000001);/* Wait 4 cycles of the slowest of PLLOUT or reference clock source (CLKIN).*/for (i=0 ; i<100 ; i++);/*In PLLCTL, write PLLRST = 1 (PLL is reset).*/*(int *)PLLCTL_1 |= 0x00000008;/*If necessary, program PREDIV and PLLM.*/*(int *)PLLM_1 = PLLM_val – 1;*(int *)PREDIV_1 = (PREDIV_val – 1) | 0x8000; /* set PLLDIV0 *//*If necessary, program PLLDIV1n. Note that you must apply the GO operationto change these dividers to new ratios.*/
/* Check that the GOSTAT bit in PLLSTAT is cleared to show that no GO operation is currently in progress.*/while( (*(int *)PLLSTAT_1) & 0x00000001);

/* Program the RATIO field in PLLDIVn to the desired new divide-down rate. If the RATIO field changed, the PLL controller will flag the changein the corresponding bit of DCHANGE.*/*(int *)PLLDIV4_1 = (PLLDIV4_val – 1) | 0x8000; /* set PLLDIV4 */*(int *)PLLDIV5_1 = (PLLDIV5_val – 1) | 0x8000; /* set PLLDIV5 */
/* Set the GOSET bit in PLLCMD to initiate the GO operation to changethe divide values and align the SYSCLKs as programmed.*/*(int *)PLLCMD_1 |= 0x00000001;
/* Read the GOSTAT bit in PLLSTAT to make sure the bit returns to 0to indicate that the GO operation has completed.*/while( (*(int *)PLLSTAT_1) & 0x00000001);
/* Wait for PLL to properly reset.(128 CLKIN1 cycles).*/for (i=0 ; i<1000 ; i++);
/* In PLLCTL, write PLLRST = 0 to bring PLL out of reset.*/*(int *)PLLCTL_1 &= ~(0x00000008);
/* Wait for PLL to lock (2000 CLKIN1 cycles). */for (i=0 ; i<4000 ; i++);
/* In PLLCTL, write PLLEN = 1 to enable PLL mode. */*(int *)PLLCTL_1 |= (0x00000001);
printf("PLL1 has been configured.\n");}else{printf("Pre-divider value must be between 1 and 32.\n","Output",2);}}else{printf("Multiplier value must be between 1 and 32.\n","Output",2);}
}

Shine：

回复 user5910726:

请问GEL打印信息是什么？

试一下在代码里能不能读写PLLM寄存器。