Jon Wilder
Active Member
For those of you who are interested in such a thing, I'm currently designing a super cool MCS-51 motherboard. I was originally going to hard solder an Atmel AT89S8253 to the board (which is like an 80C52 with an SPI port, 12K Code/2K Data EEPROM, dual data pointers and a UART with Address Recognition and ISP compatible), but am now considering socketing the main controller to make it compatible with any and all 40-pin PDIP MCS-51 derivatives.
This board will have 9 pin single row headers on ports 1 & 3 (9th pin on each port will be Vss) and Ports 0 & 2 will be on a 20 pin dual row shrouded male header. The RD and WR pins from Port 3 will also be available on this header. This will allow the user to use Ports 0 and 2 as either conventional I/O ports OR as an external peripheral buss through the use of movx instructions. As the design stands now, an external bussed resistor network will be needed to use Port 0 as conventional I/O for pull up, but I'm considering including this on the board as well to eliminate the need for it.
The board will also have the EA pin jumper settable and will include a 32K EPROM chip for code as well as an 8K external RAM chip along with the address latch. The jumper will allow the user to select either just the 32K external code chip or have some of the code on-chip with the rest of the code off chip. ROMless devices will also work on this board as well but the jump will need to be set to use just the off chip EPROM.
The crystal on the board I would use a 12MHz, but I can leave the crystal off so the user can decide what crystal they want to use on it since some like to use 11.059MHz for 9600 baud projects.
As it would only be cost effective to order these boards in runs of 10 or more, I'm curious to see if anyone else here would be interested in purchasing such a board. If anyone would be interested in one of these "motherboards", feel free to post up.
This board will have 9 pin single row headers on ports 1 & 3 (9th pin on each port will be Vss) and Ports 0 & 2 will be on a 20 pin dual row shrouded male header. The RD and WR pins from Port 3 will also be available on this header. This will allow the user to use Ports 0 and 2 as either conventional I/O ports OR as an external peripheral buss through the use of movx instructions. As the design stands now, an external bussed resistor network will be needed to use Port 0 as conventional I/O for pull up, but I'm considering including this on the board as well to eliminate the need for it.
The board will also have the EA pin jumper settable and will include a 32K EPROM chip for code as well as an 8K external RAM chip along with the address latch. The jumper will allow the user to select either just the 32K external code chip or have some of the code on-chip with the rest of the code off chip. ROMless devices will also work on this board as well but the jump will need to be set to use just the off chip EPROM.
The crystal on the board I would use a 12MHz, but I can leave the crystal off so the user can decide what crystal they want to use on it since some like to use 11.059MHz for 9600 baud projects.
As it would only be cost effective to order these boards in runs of 10 or more, I'm curious to see if anyone else here would be interested in purchasing such a board. If anyone would be interested in one of these "motherboards", feel free to post up.