数字时钟 VHDL实现，可调节时分秒，在QUATTUS||9.0下编写，可在9.0及以上版本运行并下载，芯片为Altera的Cyclone3 EP3C8T1-Digital clock VHDL realization, minutes and seconds can be adjusted in QUATTUS | | 9.0 under preparation, can be run in the 9.0 and above versions and download, chips for