Chapter 28 The DRAM Controller

This chapter describes a state machine to control a Dynamic Random Access Memory. The connection between the processor, the DRAM, and the controller typically looks like the diagram in Figure 28-1, where the data bus is connected directly to the DRAM. The Row Address Strobe (RAS) and Column Address Strobe (CAS) to the DRAM, and the Acknowledge input to the processor (ACK) are derived from the processor Address Strobe (AS) by the controller. Also, the controller must include a periodic refresh of the DRAM using the RAS and CAS inputs. Note that the Read/Write signal goes through the controller. In many cases, this signal can be connected directly to the DRAM. However, some DRAMs require that the Read/Write signal ...

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