PIC RAM Interface

[ScaleRobotics]

I have an application that I would like to distribute the processing between multiple PICs. One PIC to create output values and another to receive data from other sources.

Just curious why you need two PICs to do that. A couple people pointed to these types of devices for fast writes. And some of them are good for a 100 trillion read/writes (wonder who had to count those). http://www.ramtron.com/products/nonv...ry/serial.aspx (The 3volt type are even faster)

Ramtron FM24W256
256Kbit Ferroelectric Nonvolatile RAM
• Organized as 32,768 x 8 bits
• High Endurance 100 Trillion (1e14) Read/Writes
• 38 year Data Retention
• NoDelay™ Writes
• Advanced High-Reliability Ferroelectric Process

Fast Two-wire Serial Interface
• Up to 1 MHz Maximum Bus Frequency
• Supports Legacy Timing for 100 kHz & 400 kHz

Low Power Operation
• Wide Voltage Operation 2.7V-5.5V
• 100 uA Active Current (100 kHz)
• 15 uA Standby Current (typ.)

Industry Standard Configuration
• Industrial Temperature -40°C to +85°C
• 8-pin SOIC (-G)
• 8-pin EIAJ SOIC (-EG)

Ordering Information
• FM24W256-G (8-pin "Green"/RoHS SOIC)
• FM24W256-EG (8-pin "Green"/RoHS EIAJ SOIC)

[cncmachineguy]

I'm pretty sure I2C will be too slow. Even if you could take advantage of the 1Mhz bus timing, you state the "output PIC" will be operating in the uS time frame. I take this to mean you will be doing something every couple uS or so. It will take at least 20 or so bits per memory access (address + command + data)at 1Mhz thats 20uS. Not to mention having issues finding devices to support the 1Mhz bus speed. So that puts you at 400K, now your timing just got 60% slower.

[cc1984]

Just curious why you need two PICs to do that. A couple people pointed to these types of devices for fast writes. And some of them are good for a 100 trillion read/writes (wonder who had to count those). http://www.ramtron.com/products/nonv...ry/serial.aspx (The 3volt type are even faster)

Ramtron FM24W256
256Kbit Ferroelectric Nonvolatile RAM
• Organized as 32,768 x 8 bits
• High Endurance 100 Trillion (1e14) Read/Writes
• 38 year Data Retention
• NoDelay™ Writes
• Advanced High-Reliability Ferroelectric Process

Fast Two-wire Serial Interface
• Up to 1 MHz Maximum Bus Frequency
• Supports Legacy Timing for 100 kHz & 400 kHz

Low Power Operation
• Wide Voltage Operation 2.7V-5.5V
• 100 uA Active Current (100 kHz)
• 15 uA Standby Current (typ.)

Industry Standard Configuration
• Industrial Temperature -40°C to +85°C
• 8-pin SOIC (-G)
• 8-pin EIAJ SOIC (-EG)

Ordering Information
• FM24W256-G (8-pin "Green"/RoHS SOIC)
• FM24W256-EG (8-pin "Green"/RoHS EIAJ SOIC)

I was planning to use one pic to collect data and populate the memory and then let the other (the one creating the output) keep banging away without having to wait to collect data. I considered looking a the propeller chip to do this, but thought I would try multiple PICs running simultaneously to do the trick. The timing is an issue because I am creating a weather radar simulation that creates weather pattern returns. I have a 5us trigger pulse and then use a dac to create a waveform to represent the return pattern, this repeats every 5000us. Sounds like accessing external memory is going to be too slow.
Thanks.