In the development and research of chips, FPGA verification plays a crucial role. Efficient utilization of FPGA resources and proper pin assignment are key considerations that significantly impact the overall design. A common approach is to let synthesis tools automatically allocate resources based on timing constraints. However, this method may not always be ideal, especially when considering time-to-market during the development phase. RTL verification and board design must proceed in parallel, meaning that the pin assignment needs to be completed before the actual design code is written. As a result, the process becomes more manual, requiring careful planning and decision-making.
**Consider the following aspects:**
1. **Signal flow within the FPGA logic.**
FPGAs used for IC verification typically have large logic capacity and a high number of I/O pins. When assigning pins, it's essential to consider how signals will be routed on the PCB. Poor pin assignment can lead to excessive signal crossovers, making routing difficult or even impossible. In some cases, even if the board is functional, timing issues may arise due to long external delays. Therefore, it’s important to understand the working environment of the FPGA and identify where each signal originates. Signals should be assigned to the nearest available I/O pin, following the principle of shortest connection, especially within the same BANK.
2. **Understand the internal BANK structure of the FPGA.**
Modern FPGAs are divided into multiple BANKs, each with different numbers of I/O pins and supported I/O standards. For example, in Altera’s Stratix II series, the distribution of BANKs and their supported I/O standards vary. This information is critical for effective pin assignment. By understanding the layout of each BANK and aligning it with the signal flow, you can ensure that related signals are grouped together, improving both performance and routability.
3. **Know the I/O standards supported by each BANK.**
Different BANKs support various I/O standards. It's important to assign pins that require the same standard to the same BANK, as most BANKs cannot support multiple I/O standards simultaneously. While there may be exceptions, it’s necessary to check the specifications of the I/O standards to avoid conflicts.
4. **Pay attention to special signals such as clocks and resets.**
Clock and reset signals are critical for synchronization and stability. Clocks should ideally be assigned to global clock pins to minimize delay and maximize drive strength. Resets usually benefit from strong driving capabilities and good synchronization, so they are often connected to the same global clock pin. When dealing with multiple clocks, especially differential ones, it's important to follow manufacturer guidelines. For instance, in Xilinx FPGAs, paired differential clocks (P and N) should not be assigned to the same bank if they’re intended for different purposes, as this can cause conflicts.
5. **Consider signal integrity.**
During pin assignment, bus signals often flip simultaneously, which can lead to signal integrity issues like crosstalk and noise. To mitigate these problems, it's advisable to separate signals that switch at the same time, ensuring better signal quality and system reliability.
Infrared Pen,Infrared Touch Pen,Infrared Tablet Stylus Pen,Infrared Stylus Pencil
Shenzhen Ruidian Technology CO., Ltd , https://www.wisonen.com