Try this for stopwatch counter timer.
Timing Counter 技术资料
汇集 Timing Counter 相关的电路原理图、PCB工程文件、单片机/FPGA源代码、数据手册与应用设计方案。
an up down counter in verilog
an up down counter for AVR
89C51 based counter program 5 Digit
counter of modulus 10 with LED
The Simulation Symbol Timing Synchronization using Matlab
OPENGL animation timing tutorial using LWJGL engine.
altera的timing约束文档,很有帮助
example for F-counter soft with PIC16F84A
source code of counter,ram,lfsr etc