Clock routing resources are characterized by high speed and low SKEW, which is very important for system design. Even if the system speed is not high, you should pay attention to the clock design to eliminate the potential clock hazard. The Spartan-6 device contains 16 global clock resources and 40 I/O area clock resources. The global clock is used for the system clock, while the I/O area clock is dedicated to the I/O serial/deserial (ISERDES and OSERDES) designs. The Spartan-6 clock resource contains the following four types. Global clock input pin (GCLK). Bureau clock multiplexer. I/O clock buffer. Clock wiring network. It includes a global clock network driven by BUFGMUX and an I/O area clock network driven by I/O clock buffer (BUFIO2) and PLL clock buffer (BUFPLL). First, the clock input Each Spartan-6 has 32 global clock input pins distributed around the FPGA. The distribution of the clock input pins on the chip is shown in Figure 2-5. The clock input pin receives the external clock signal and is directly connected to the on-chip DCM/PLL/BUFGMUX/BUFIO2. When the clock input pin is not connected to the clock, it is used as a normal I/O. A differential clock input requires two global clock inputs. The paired clock inputs are consecutive on the label. For example, GCLK0 and GCLK1 are differential pairs, and GCLK20 and GCLK21 are differential pairs. Each global clock buffer has two clock inputs, and the Spartan-6 supports up to 16 pairs of differential global clock inputs. The clock input pin in the design is connected to the IBUFG primitive. Usually, the synthesis tool analyzes the design and automatically pushes the top-level clock pin to connect to IBUFG. If more IBUFG control functions are needed, IBUFG's I port can be connected to the top-level port and the O port can be connected to DCM, BUFG or general logic by instantiating IBUFG. Figure 2-5 Distribution diagram of the clock input pin on the chip Stainless Steel Pipe,Medical Ss Capillary Pipe,Stainless Steel Tubes,Seamless Presion Stainless Steel Tube ShenZhen Haofa Metal Precision Parts Technology Co., Ltd. , https://www.haofametal.com