A bank of memory (flash or RAM) consists of all those memory chips on your system that are controlled by the same chip select signal.
For example, a system might consist of one flash chip with a 8 bit bus interface, which is attached to the CS0 chip select signal, 2 flash chips with a 16 bit bus interface, which are attached to the CS1 chip select signal, and 2 SDRAM chips with a 16 bit bus interface, which are attached to the CS2 chip select signal.
This setup results in a system with 3 banks of memory:
一个bank包含在同一个片选信号控制下的存储芯片。