CDCE913产生任意频率

1,上TI官网下载CDCE913的datasheet和配置软件clock Pro。如果只需要配置CDCE913成某一个固定频率，那么用clock Pro可以很方便快捷。http://www.ti.com.cn/general/cn/docs/lit/getliterature.tsp?baseLiteratureNumber=scac119&fileType=zip

TI的初衷应该就是通过I2C配置几个频率，然后写入到EEPROM中，不然没有必要设计EEPROM和频率选择PIN(S1,S2）。

该软件产生的配置文件是二进制的csv或者txt文档，导入到Excel中处理成16进制即可。或者直接手动填写，反正也就20来个寄存器。

2，如需要在程序运行过程中动态的配置成不同的频率，那么你需要通过I2C接口配置。CDCE913的器件地址如下：

#define CDCE_ADDRESS 0x65

#define SLAVE_WRITE CDCE_ADDRESS<<1
#define SLAVE_READ ((CDCE_ADDRESS<<1) | 0x01)

3，了解一下配置原理

可以看到Y1,Y2,Y3都可以从PLL1配置，然后进过M(M1,M2,M3)，Pdiv出来。寄存器配置完成后，需要拉高S0，才能使能输出。

4，查看datasheet，配置PLL需要配置以下参数

计算方法如下：

公式略微有点复杂。下面代码以配置Y1输出为例（输入晶振频率为8MHz，平台为STM32，I2C为软件模拟）。

#define CLK_IN 8
void CDCE_Init(uint16_t f_out) { uint8_t read_back; uint8_t i = 1; AckTypeDef ack; uint32_t M, N, Pdiv, Q, R; uint8_t reg18, reg19, reg1A, reg1B; int P; uint16_t f_vco = f_out; bool result = false; uint8_t f_range;
while (f_vco < 80) { i++; f_vco = f_out * i; }
while (f_vco < 231) { for (N = 4095; N > 0; N–) { for (M = 511; M > 0; M–) { if ((N * CLK_IN / M) == f_vco) { { result = true; break; } } } if (result) { break; } } if (result) { break; } else { i++; f_vco = f_out * i; } }
if (!result) { UserPrintf("Error:unsupport pclk\n"); return; }
P = 4 – (int)((log((double)N / (double)M))/log(2)); if (P < 0) { P = 0; } Q = (int)((double)N * pow(2, (double)P) / (double)M); R = (double)N * pow(2, (double)P) – M * Q;
if (f_vco < 125) { f_range = 0; } else if ((f_vco >= 125) && (f_vco < 150)) { f_range = 1; } else if ((f_vco >= 150) && (f_vco < 175)) { f_range = 2; } else { f_range = 3; }
S0 = 0;
ack = CDCE_Read8bit(0x00, 1, &read_back); if (ack != I2C_ACK) { UserPrintf("Error:clk configuration failed , maybe no pullup res\n"); return; }
if (read_back != CDCE_ID) { UserPrintf("Error:clk device ID error\n"); return; }
Pdiv = f_vco / f_out;
UserPrintf("M:%d,N:%d,Pdiv:%d,f_vco:%d,P:%d,Q:%d,R:%d\n", M, N, Pdiv,f_vco,P,Q, R);
CDCE_WriteByte(0x02, 0xB4); CDCE_WriteByte(0x03, (uint8_t)Pdiv); CDCE_WriteByte(0x04, 0x02); CDCE_WriteByte(0x05, 0x00); CDCE_WriteByte(0x06, 0x40); CDCE_WriteByte(0x12, 0x00); CDCE_WriteByte(0x13, 0x01); CDCE_WriteByte(0x14, 0x6D); CDCE_WriteByte(0x15, 0x02); CDCE_WriteByte(0x16, 0); CDCE_WriteByte(0x17, 0);
reg18 = (N >> 4) & 0xFFF; reg19 = (N & 0xf) << 4 | (R & 0xf0) >> 5; reg1A = (R & 0x1f) << 3 | ((Q >> 3) & 0x7); reg1B = (Q & 0x7) << 5 | (P & 0x07) << 2 | (f_range & 0x03);
CDCE_WriteByte(0x18, reg18); CDCE_WriteByte(0x19, reg19); CDCE_WriteByte(0x1A, reg1A); CDCE_WriteByte(0x1B, reg1B);
CDCE_WriteByte(0x1C, N); CDCE_WriteByte(0x1D, ((N & 0xf) << 4) | (R & 0xf0)); CDCE_WriteByte(0x1E, (R & 0x0f) | (Q & 0xf0)); CDCE_WriteByte(0x1F, ((Q & 0x07) << 5) | ((P & 0x07) << 2) | (f_range & 0x03));
S0 = 1; UserPrintf("Info:clk well configured\n"); }