MMCM与PLL

​ UltraScale器件中时钟管理模块(CMT)包含mixed-mode clock manager (MMCM) 和phase-locked loops (PLLs) 。PLL主要用来生成I/O时钟，也包含一部分MMCM的功能。

​ 其中MMCM输出时钟相位调整语VCO频率相关。

MMCME4_ADV原语

​ MMCM原语包含MMCME3_BASE和MMCME3_ADV，在UltraScale+ 器件中MMCME4替代MMCME3。UltraScale+ 器件MMCM原语包含MMCME4_BASE和MMCME4_ADV。

​ MMCME4_BASE实现基本MMCM功能。MMCME4_ADV除了能实现MMCME4_BASE功能外，还可以实现动态可重配等功能。

计算输出时钟频率

​ 时钟输出频率和VCO输出频率计算公式如下，其中M值通过CLKFBOUT_MULT_F设置，D值通过DIVLK_DIVIDE设置，O的值为通过CLKOUT_DIVIDE.设置。

​ 下图代码中CLKFBOUT_MULT_F设置成8，DIVCLK_DIVIDE设置成1，CLKOUT0_DIVIDE_F设置成4，输入时钟频率CLKIN1_PERIOD等于10，为100Mhz。通过公式计算CLKOUT0输出为100*8/4=200Mhz。

MMCME4_ADV #(
      .BANDWIDTH("OPTIMIZED"),        // Jitter programming
      .CLKFBOUT_MULT_F(8),          // Multiply value for all CLKOUT
      .CLKFBOUT_PHASE(0.0),           // Phase offset in degrees of CLKFB
      .CLKFBOUT_USE_FINE_PS("FALSE"), // Fine phase shift enable (TRUE/FALSE)
      .CLKIN1_PERIOD(10),            // Input clock period in ns to ps resolution (i.e., 33.333 is 30 MHz).
      .CLKIN2_PERIOD(0.0),            // Input clock period in ns to ps resolution (i.e., 33.333 is 30 MHz).
      .CLKOUT0_DIVIDE_F(4),         // Divide amount for CLKOUT0
      .CLKOUT0_DUTY_CYCLE(0.5),       // Duty cycle for CLKOUT0
      .CLKOUT0_PHASE(0.0),            // Phase offset for CLKOUT0
      .CLKOUT0_USE_FINE_PS("FALSE"),  // Fine phase shift enable (TRUE/FALSE)
      .CLKOUT1_DIVIDE(1),             // Divide amount for CLKOUT (1-128)
      .CLKOUT1_DUTY_CYCLE(0.5),       // Duty cycle for CLKOUT outputs (0.001-0.999).
      .CLKOUT1_PHASE(0.0),            // Phase offset for CLKOUT outputs (-360.000-360.000).
      .CLKOUT1_USE_FINE_PS("FALSE"),  // Fine phase shift enable (TRUE/FALSE)
      .CLKOUT2_DIVIDE(1),             // Divide amount for CLKOUT (1-128)
      .CLKOUT2_DUTY_CYCLE(0.5),       // Duty cycle for CLKOUT outputs (0.001-0.999).
      .CLKOUT2_PHASE(0.0),            // Phase offset for CLKOUT outputs (-360.000-360.000).
      .CLKOUT2_USE_FINE_PS("FALSE"),  // Fine phase shift enable (TRUE/FALSE)
      .CLKOUT3_DIVIDE(1),             // Divide amount for CLKOUT (1-128)
      .CLKOUT3_DUTY_CYCLE(0.5),       // Duty cycle for CLKOUT outputs (0.001-0.999).
      .CLKOUT3_PHASE(0.0),            // Phase offset for CLKOUT outputs (-360.000-360.000).
      .CLKOUT3_USE_FINE_PS("FALSE"),  // Fine phase shift enable (TRUE/FALSE)
      .CLKOUT4_CASCADE("FALSE"),      // Divide amount for CLKOUT (1-128)
      .CLKOUT4_DIVIDE(1),             // Divide amount for CLKOUT (1-128)
      .CLKOUT4_DUTY_CYCLE(0.5),       // Duty cycle for CLKOUT outputs (0.001-0.999).
      .CLKOUT4_PHASE(0.0),            // Phase offset for CLKOUT outputs (-360.000-360.000).
      .CLKOUT4_USE_FINE_PS("FALSE"),  // Fine phase shift enable (TRUE/FALSE)
      .CLKOUT5_DIVIDE(8),             // Divide amount for CLKOUT (1-128)
      .CLKOUT5_DUTY_CYCLE(0.5),       // Duty cycle for CLKOUT outputs (0.001-0.999).
      .CLKOUT5_PHASE(0.0),            // Phase offset for CLKOUT outputs (-360.000-360.000).
      .CLKOUT5_USE_FINE_PS("FALSE"),  // Fine phase shift enable (TRUE/FALSE)
      .CLKOUT6_DIVIDE(1),             // Divide amount for CLKOUT (1-128)
      .CLKOUT6_DUTY_CYCLE(0.5),       // Duty cycle for CLKOUT outputs (0.001-0.999).
      .CLKOUT6_PHASE(0.0),            // Phase offset for CLKOUT outputs (-360.000-360.000).
      .CLKOUT6_USE_FINE_PS("FALSE"),  // Fine phase shift enable (TRUE/FALSE)
      .COMPENSATION("AUTO"),          // Clock input compensation
      .DIVCLK_DIVIDE(1),              // Master division value
      .IS_CLKFBIN_INVERTED(1'b0),     // Optional inversion for CLKFBIN
      .IS_CLKIN1_INVERTED(1'b0),      // Optional inversion for CLKIN1
      .IS_CLKIN2_INVERTED(1'b0),      // Optional inversion for CLKIN2
      .IS_CLKINSEL_INVERTED(1'b0),    // Optional inversion for CLKINSEL
      .IS_PSEN_INVERTED(1'b0),        // Optional inversion for PSEN
      .IS_PSINCDEC_INVERTED(1'b0),    // Optional inversion for PSINCDEC
      .IS_PWRDWN_INVERTED(1'b0),      // Optional inversion for PWRDWN
      .IS_RST_INVERTED(1'b0),         // Optional inversion for RST
      .REF_JITTER1(0.0),              // Reference input jitter in UI (0.000-0.999).
      .REF_JITTER2(0.0),              // Reference input jitter in UI (0.000-0.999).
      .SS_EN("FALSE"),                // Enables spread spectrum
      .SS_MODE("CENTER_HIGH"),        // Spread spectrum frequency deviation and the spread type
      .SS_MOD_PERIOD(10000),          // Spread spectrum modulation period (ns)
      .STARTUP_WAIT("FALSE")          // Delays DONE until MMCM is locked
   )
   MMCME4_ADV_inst (
      .CDDCDONE(),         // 1-bit output: Clock dynamic divide done
      .CLKFBOUT(clk_fb),         // 1-bit output: Feedback clock
      .CLKFBOUTB(),       // 1-bit output: Inverted CLKFBOUT
      .CLKFBSTOPPED(), // 1-bit output: Feedback clock stopped
      .CLKINSTOPPED(), // 1-bit output: Input clock stopped
      .CLKOUT0(clkout0),           // 1-bit output: CLKOUT0
      .CLKOUT0B(),         // 1-bit output: Inverted CLKOUT0
      .CLKOUT1(clkout1),           // 1-bit output: CLKOUT1
      .CLKOUT1B(),         // 1-bit output: Inverted CLKOUT1
      .CLKOUT2(clkout2),           // 1-bit output: CLKOUT2
      .CLKOUT2B(),         // 1-bit output: Inverted CLKOUT2
      .CLKOUT3(clkout3),           // 1-bit output: CLKOUT3
      .CLKOUT3B(),         // 1-bit output: Inverted CLKOUT3
      .CLKOUT4(clkout4),           // 1-bit output: CLKOUT4
      .CLKOUT5(clkout5),           // 1-bit output: CLKOUT5
      .CLKOUT6(clkout6),           // 1-bit output: CLKOUT6
      .DO(),                     // 16-bit output: DRP data output
      .DRDY(),                 // 1-bit output: DRP ready
      .LOCKED(lock),             // 1-bit output: LOCK
      .PSDONE(),             // 1-bit output: Phase shift done
      .CDDCREQ(1'b0),           // 1-bit input: Request to dynamic divide clock
      .CLKFBIN(clk_fb_g),           // 1-bit input: Feedback clock
      .CLKIN1(clk_in),             // 1-bit input: Primary clock
      .CLKIN2(1'b0),             // 1-bit input: Secondary clock
      .CLKINSEL(1'b1),         // 1-bit input: Clock select, High=CLKIN1 Low=CLKIN2
      .DADDR(7'b0),               // 7-bit input: DRP address
      .DCLK(1'b0),                 // 1-bit input: DRP clock
      .DEN(1'b0),                   // 1-bit input: DRP enable
      .DI(16'b0),                     // 16-bit input: DRP data input
      .DWE(1'b0),                   // 1-bit input: DRP write enable
      .PSCLK(1'b0),               // 1-bit input: Phase shift clock
      .PSEN(1'b0),                 // 1-bit input: Phase shift enable
      .PSINCDEC(1'b0),         // 1-bit input: Phase shift increment/decrement
      .PWRDWN(1'b0),             // 1-bit input: Power-down
      .RST(rst)                    // 1-bit input: Reset
   );

使用全局时钟网络

​ 如下图所示，CLKOUT0输出要经过全局时钟网络BUFG，CLKFBOUT通过BUFG反馈到CLKFBIN。

代码如下：

BUFG u_clkout0
   (
   .O (clk_out0_g),
   .I (clkout0)  
   ); 
 BUFG u_clk_fb
   (
   .O (clk_fb_g),
   .I (clk_fb)  
   ); 

PLL4_ADV

​ UltraScale+ 器件包含PLL4_BASE和PLL4_ADV。

​ PLL4_ADV原语输出时钟频率计算方式与MMCME4_ADV一样。输入时钟周期为5ns，频率200Mhz，CLKFBOUT_MULT_F设置成4，DIVCLK_DIVIDE设置成1，CLKOUT0_DIVIDE_F设置成4，CLKOUT0输出依然为200Mhz。

 PLLE4_ADV #(
      .CLKFBOUT_MULT(4),          // Multiply value for all CLKOUT
      .CLKFBOUT_PHASE(0.0),       // Phase offset in degrees of CLKFB
      .CLKIN_PERIOD(5),         // Input clock period in ns to ps resolution (i.e., 33.333 is 30 MHz).
      .CLKOUT0_DIVIDE(4),         // Divide amount for CLKOUT0
      .CLKOUT0_DUTY_CYCLE(0.5),   // Duty cycle for CLKOUT0
      .CLKOUT0_PHASE(0.0),        // Phase offset for CLKOUT0
      .CLKOUT1_DIVIDE(1),         // Divide amount for CLKOUT1
      .CLKOUT1_DUTY_CYCLE(0.5),   // Duty cycle for CLKOUT1
      .CLKOUT1_PHASE(0.0),        // Phase offset for CLKOUT1
      .CLKOUTPHY_MODE("VCO_2X"),  // Frequency of the CLKOUTPHY
      .COMPENSATION("AUTO"),      // Clock input compensation
      .DIVCLK_DIVIDE(1),          // Master division value
      .IS_CLKFBIN_INVERTED(1'b0), // Optional inversion for CLKFBIN
      .IS_CLKIN_INVERTED(1'b0),   // Optional inversion for CLKIN
      .IS_PWRDWN_INVERTED(1'b0),  // Optional inversion for PWRDWN
      .IS_RST_INVERTED(1'b0),     // Optional inversion for RST
      .REF_JITTER(0.0),           // Reference input jitter in UI
      .STARTUP_WAIT("FALSE")      // Delays DONE until PLL is locked
   )
   PLLE4_ADV_inst (
      .CLKFBOUT(clk_fb),       // 1-bit output: Feedback clock
      .CLKOUT0(clk0),         // 1-bit output: General Clock output
      .CLKOUT0B(),       // 1-bit output: Inverted CLKOUT0
      .CLKOUT1(clk1),         // 1-bit output: General Clock output
      .CLKOUT1B(),       // 1-bit output: Inverted CLKOUT1
      .CLKOUTPHY(),     // 1-bit output: Bitslice clock
      .DO(),                   // 16-bit output: DRP data output
      .DRDY(),               // 1-bit output: DRP ready
      .LOCKED(lock),           // 1-bit output: LOCK
      .CLKFBIN(clk_fb_g),         // 1-bit input: Feedback clock
      .CLKIN(clk_in),             // 1-bit input: Input clock
      .CLKOUTPHYEN(1'b1), // 1-bit input: CLKOUTPHY enable
      .DADDR(7'b0),             // 7-bit input: DRP address
      .DCLK(1'b0),               // 1-bit input: DRP clock
      .DEN(1'b0),                 // 1-bit input: DRP enable
      .DI(16'b0),                   // 16-bit input: DRP data input
      .DWE(1'b0),                 // 1-bit input: DRP write enable
      .PWRDWN(1'b0),           // 1-bit input: Power-down
      .RST(rst)                  // 1-bit input: Reset
   );

使用方法

OSERDESE3 时钟

当MMCME4_ADV输出时钟作为OSERDESE3输入时钟是，MMCME4_ADV输出时钟通过BUFGCE和BUFGCE_DIV后，进入OSERDESE3。通过BUFGCE和BUFGCE_DIV来减少CLK与CLKDIV之间时钟偏差。