On Thu, 2 Nov 1995, PETE KLAMMER said: Subject: : 32Kbyte NV FRAMs? > > From: Don McKenzie > > Subject: Re: 512 KByte of memory: EASIEST WAY!!! > > > > He said 512 Kilobytes!! -------------clip---------clip----------------------------- > Well, for adequate density/capacity, for one, eh? Sorry if I got anyone's > hopes up. -------------clip---------clip----------------------------- Hi, I have been following your threads on interfacing 512K x 8 memory to PICs. I have Dallas Semiconductor's 11 page data sheet for their 3 wire to bytewide bus interface 1280.ps (370k). The chip has the following features: * Adapts JEDEC bytewide memory to a 3-wire serial port * Supports 512k bytes of memory * 80-pin version provides arbitration mechanisms for dual port operation * CMOS circuitry for battery backup and battery operate applications * Cyclic redundancy check monitors serial transmission for error * Available in 44/80 pin quad flat pack for high density requirements A short description from data sheet page 1, is as follows: The DS1280 adds a 3-wire serial port to a bytewide static RAM, yet maintains the existing bytewide port. Memory capacity of up to 512K x 8 bytes can be addressed directly. Arbitration between the serial and bytewide port is accomplished by handshaking or using predictable idle time as an access window. The serial protocol requires a 6 byte protocol to set up memory transfers. Cyclic redundancy check circuitry is included to monitor serial data transmission error. The 3-wire serial port will correctly read and write any byte wide static RAM with an effective access time of 200ns. The serial interface uses bi-directional data pin (DQ), unlike other three/four wire interfaces which have separate Data In and Data Out pins. Data pins description follows: ___ RST RESET FOR SERIAL PORT Clk CLOCK INPUT FOR SERIAL PORT DQ DATA INPUT/OUTPUT FOR SERIAL PORT DQOE SERIAL PORT ACTIVE OUTPUT *AVAILABLE ONLY ON 44 PIN VERSION DQE SERIAL PORT ACTIVE OUTPUT *AVAILABLE ONLY ON 80 PIN VERSION ___ CEB SYSTEM BUS ENABLE *AVAILABLE ONLY ON 80 PIN VERSION ___ OEB SYSTEM BUS READ ENABLE *AVAILABLE ONLY ON 80 PIN VERSION ___ WEB SYSTEM BUS WRITE ENABLE *AVAILABLE ONLY ON 80 PIN VERSION A0B-A18B SYSTEM ADDRESS BUS *AVAILABLE ONLY ON 80 PIN VERSION D0B-D7B SYSTEM DATA BUS *AVAILABLE ONLY ON 80 PIN VERSION ___ CER RAM CHIP ENABLE ___ WER RAM WRITE ENABLE ___ OER RAM OUTPUT ENABLE A0R-A18R RAM ADDRESS BUS D0R-D7R RAM DATA BUS GND GROUND Vcc 5 VOLTS ---------------------------------------------------------------------------- ------ As you can see it is able to both access NV static ram, and the 80 pin version can allow access to system bus of another cpu. It appears to be good choice to expand an existing PIC design, which may have a serial interface already implemented, but other I/O pins commited to other tasks. It makes at most a single chip solution to expand a PIC or any 8 bit cpu to access additional ram. Dallas also has chips that combine the features for cpu/ram reset for power down or brown-out protection, with a real time clock that runs on 3V lithium power cells when your cpu/ram is in sleep mode. Dallas also have plug-in non/volatile read write cartridge with size up to 512K x 8 byte, which is ideal for data-logging. It can be inserted or removed by non-technical persons. It has manual read/write enable switch in cartridge, and has hot swap feature built-in. It is DS1217M, data sheet is 1217M.PS (postscript). You can retrieve full data sheets as well as application notes for these and other chips at: ftp.dalsemi.com/pub/datasheets/ regards ******************************************************************************** * Tom Brown E-Mail:tombrown@indo.net.id * * Bumi Karang Indah Phone: 62-21-7508264 * * Jalan Karang Asri II, ************************************************** * Blok C2/#43, Lebak Bulus * "If something is worth doing, * * Jakarta, Seletan 12440 * It's worth doing right the first time" * * Indonesia * * ********************************************************************************