电子电路 L13- RAM& ROM Based Digital Design(1) - 图文 

RAM & ROM Based Digital DesignECE 152A –Winter 2012Reading Assignment??Brown and Vranesic??10 Digital System Design??10.1 Building Block Circuits??10.1.3 Static Random Access Memory (SRAM)??10.1.4 SRAM Blocks in PLDsMarch 12, 2012ECE 152A -Digital Design Principles21Reading Assignment??Roth??9 Multiplexers, Decoders, and Programmable Logic Devices??9.5 Read Only MemoriesMarch 12, 2012ECE 152A -Digital Design Principles3Read/Write Memories??RAM??Random Access Memory??Same access time to all memory locations??As opposed to serial access memory??About the same time for read and write??SRAM??Static Random Access Memory??Built with cross coupled inverters and pass transistorsMarch 12, 2012ECE 152A -Digital Design Principles42Read/Write Memories??6T SRAM Cell??CMOS implementation with pass transistors??Sense amp at bottom of columnMarch 12, 2012ECE 152A -Digital Design Principles5Read/Write Memories??RAM Blocks and Register FilesMarch 12, 2012ECE 152A -Digital Design Principles63Read/Write Memories??RAM (cont)??DRAM??Uses capacitance on MOSFET gate??Must be “refreshed”periodically??Restore charge on gate capacitance??Accomplished by reading or writing to memory locationMarch 12, 2012ECE 152A -Digital Design Principles7Read/Write Memories??RAM (cont)??Both SRAM and DRAM are “volatile”??Data lost when power is removed??DRAM has approximately 4 times the capacity of SRAM??Basic memory cell of DRAM is smaller??~2 transistors vs. 6??SRAM is generally fasterMarch 12, 2012ECE 152A -Digital Design Principles84Read Only Memories??ROM, PROM, EPROM, EEPROM, EAROM??Not in-system writeable ??Except by special means, i.e. non-standard voltages and timing??“Non-volatile”??Data retained when power removed??ROM : Read Only Memory??Mask programmed by manufacturer??Not erasable (programming permanent)??High volume applicationsMarch 12, 2012ECE 152A -Digital Design Principles9Read Only Memories??ROM, PROM, EPROM, EEPROM, EAROM??PROM : Programmable Read Only Memory??Programmed by user??Also not erasable??EPROM : Erasable Programmable Read Only Memory??Programmed by user??Erased using UV light??“erase”sets all bits to 0 or 1??Development applicationsMarch 12, 2012ECE 152A -Digital Design Principles105