I need some help.
After several years retired and many more years away from cobbling together TTL and field programmable parts, I'm trying to get my hands dirty again on a project.
I am trying to design a replacement UART module for a radio designed about 25 years ago. The original module used a Phillips SCN2661A UART. That one is not manufactured or available anymore. The closest available replacement is the SCN68661 which I can only get in small quantities in the 68661B version. "B" is different than "A" in the Baud Rates provided.
I thought it might be feasible to use a PIC which includes a UART to build a replacement. It looked like I could get everything I needed into one PIC. But then I looked at the instruction cycle times of 200 nSec. My requirement is to handle Reads and Writes of the CPU to UART Data and Control Registers in a fixed period of 550nSec. The PIC just can't do it.
So I would like to place all the registers in a chip or chips outside the PIC. The CPU Bus would fill and empty the registers. The PIC would asynchronously move the register data to and from the UART. The only register file chip I know about is the TTL 'LS170 which is only
4 bits by 4 bytes (and may not be available). I would have to use eight of them plus some glue logic and buffering.
So I'm looking for some kind of modern register file or small static RAM which can be addressed and written at one end and addressed and read at the other end. It would need at least 10 Bytes by 8 Bits. Setup and Hold times need to be on the order of 100nSec or less.
I appreciate all the time that the experienced contributors to this newsgroup take with answering requests like mine.
Thank You All, Ken Fowler snipped-for-privacy@Comcast.net