Power Supply & Clocking
I started the week by looking at alternative power supply designs. The problem with the current design is that it utilizes 2 bulky linear voltage regulators. There are many single chip solutions for the 3 voltage levels required. However, they are not really cost effective, thus can not be used. The final decision is to use 3 different ICs (MCP1727) in the design. MCP1727 has much higher current rating and also it is considerably smaller in size.
There are 2 different sources of clock that can be used for any peripheral. The first option is to use a peripheral clock (PBCLK) this can be driven from many sources such as the SYSCLK, POSCL, etc. This clock is software configurable through a divisor from 1 to 128. The other option is to use the reference clock which provides a more configurable frequency range. The combination of input and output divider and multiplier results in a frequency range from 0.006 to 24 times the input frequency. Thus, a wide range of frequencies can be chosen on the fly.
Memory Controller Block
The LX9 TQG144 does not have a MCB. MCB is a block which is used to as an interface between Spartan 6 and an external memory. Additional I/O pins on the FPGA can now be connected to external ports , since they are not used for a memory controller block.