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builderpages:plasmo:spx-mpu [2017/08/06 13:29]
plasmo
builderpages:plasmo:spx-mpu [2017/10/10 11:41] (current)
plasmo
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 ADC Communication's SPX-MPU board is a MC68302-based controller board for the Soneplex communication product line. This board was phased out around 2005 and large number of them were available on eBay as surplus/salvaged boards. They are still available today (2017), although at a higher price of 15-25 USD. ADC Communication's SPX-MPU board is a MC68302-based controller board for the Soneplex communication product line. This board was phased out around 2005 and large number of them were available on eBay as surplus/salvaged boards. They are still available today (2017), although at a higher price of 15-25 USD.
  
-—photo of SPX-MPU+[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:spx-mpu:adc_mpu_component_side.jpg|{{:builderpages:plasmo:spx-mpu:adc_mpu_component_side.jpg?direct&800x401}}]]Photo of SPX-MPU
  
 SPX-MPU contains: SPX-MPU contains:
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 Perhaps there is a way to upload software patch into the board, but I have no knowledge of it. In the absence of software upload, the most obvious way of changing software is to replace the boot flash with a new set of boot flash. The boot flash are located on the corner of the board above the DB25 connector. UB2 is the most significant byte and UB3 is the least significant byte. For people with the appropriate skill and equipment, UB2 and UB3 can be readily cut out and sockets installed in their place. New boot software can be programmed in an external flash programmer and installed in the sockets. The board will now boot up with the new software. The drawback with this method is that every board repurposed need to remove two flash chips, install two sockets and program two new flash chips. That's a significant effort in time and money. There is another way: Perhaps there is a way to upload software patch into the board, but I have no knowledge of it. In the absence of software upload, the most obvious way of changing software is to replace the boot flash with a new set of boot flash. The boot flash are located on the corner of the board above the DB25 connector. UB2 is the most significant byte and UB3 is the least significant byte. For people with the appropriate skill and equipment, UB2 and UB3 can be readily cut out and sockets installed in their place. New boot software can be programmed in an external flash programmer and installed in the sockets. The board will now boot up with the new software. The drawback with this method is that every board repurposed need to remove two flash chips, install two sockets and program two new flash chips. That's a significant effort in time and money. There is another way:
  
--photo of the board with sockets replacing boot flash–+[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:spx-mpu:bootflash_in_sockets.jpg|{{:builderpages:plasmo:spx-mpu:bootflash_in_sockets.jpg?direct&800x553}}]]Photo of bootflash replaced with sockets
  
-**Reprogramming headers for 68302SBC**+**Programming headers for 68302SBC**
  
-The reprogramming headers are a pair of flash chips (different manufacturer than the ones soldered on board) with the appropriate boot software programmed and then soldered to the solder tabs of PLCC sockets. This sub-assembly will fit over UB2 and UB3. A single-pole double-throw switch is wired to boot chip select and can select either the original boot flash or the reprogramming headers.+The programming headers are a pair of flash chips (different manufacturer than the ones soldered on board) with the appropriate boot software programmed and then soldered to the solder tabs of PLCC sockets. This sub-assembly will fit over UB2 and UB3. A single-pole double-throw switch is wired to boot chip select and can select either the original boot flash or the programming headers.
  
-—–Photo of reprogramming headers+[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:spx-mpu:programming_headers_installed_copy.jpg|{{:builderpages:plasmo:spx-mpu:programming_headers_installed_copy.jpg?direct&800x468}}]]Photo of programming headers installed
  
-The software works as followswitch the boot chip select to the reprogramming headers and power upMC68302 will execute the new boot software located on the reprogramming headersLoad a cloning software into the 68302SBC RAM and execute itThis cloning software will copy the boot software located on the reprogramming header into RAM and then examine the device ID of the flash continuously and wait for the switch to connect to the original boot flashOnce the switch to the original boot flash is made, the cloning software will erase the flash and copy the new boot software into the original boot flash. The repurpose of the board is now completed. This method still requires some soldering/desoldering* The smt capacitor between UB2 and UB3 needs to be removed, otherwise the headers will not fit properly * The 330 ohm resistor connecting boot chip select need to be removed and a pull up resistor installed at the flash side of the chip select+[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:spx-mpu:programming_headers_removed.jpg|{{:builderpages:plasmo:spx-mpu:programming_headers_removed.jpg?direct&800x481}}]]
  
-—photo of switchesreprogramming header installed—–+Photo of programming headers removed 
 + 
 +[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:spx-mpu:programming_header_details.jpg|{{:builderpages:plasmo:spx-mpu:programming_header_details.jpg?direct&800x416}}]] 
 + 
 +Detailed view of the programming header installed over the existing boot flash 
 + 
 +Yet another way of replacing the original boot software is to program a set of flash with the desired boot softwarestraighten the 'J' leads of the custom flash chips and position them on top of the original flash chips, solder the corresponding leads except the chip selects. A single-throw double-pole switch selects either the chip selects of the original flash chips or the chip selects of the custom flash chips. This arrangement is for boot flash software development; if boot flash software crashed and won't boot at all, the developer can switch to the custom boot flash and regain the control of the board. 
 + 
 +[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:spx-mpu:piggy_back_bootflash_copy.jpg|{{:builderpages:plasmo:spx-mpu:piggy_back_bootflash_copy.jpg?direct&800x419}}]] 
 + 
 +Photo of custom boot flash 'piggyback' over original boot flash 
 + 
 +[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:spx-mpu:piggy_back_bootflashb_copy.jpg|{{:builderpages:plasmo:spx-mpu:piggy_back_bootflashb_copy.jpg?direct&800x331}}]] 
 + 
 +Detailed view of the 'piggyback' of the custom boot flash chips 
 + 
 +---- 
 + 
 +The software for the programming headers works as follow: switch the boot chip select to the programming headers and power up. MC68302 will execute the new boot software located on the programming headers. Load a cloning software into the 68302SBC RAM and execute it. This cloning software will copy the boot software located on the programming header into RAM and then examine the device ID of the flash continuously and wait for the switch to connect to the original boot flash. Once the switch to the original boot flash is made, the cloning software will erase the flash and copy the new boot software into the original boot flash. The repurpose of the board is now completed. 
 + 
 +This method still requires some soldering/desoldering: 
 + 
 +  * The smt capacitor between UB2 and UB3 needs to be removed, otherwise the headers will not fit properly 
 +  * The 330 ohm resistor connecting boot chip select need to be removed and a pull up resistor installed at the flash side of the chip select
  
 New boot source code, S-record New boot source code, S-record
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 ADC SPX-MPU [[:builderpages:plasmo:spx-mpu:mpuschematic|schematics]] ADC SPX-MPU [[:builderpages:plasmo:spx-mpu:mpuschematic|schematics]]
 +
 +ADC SPX-MPU [[:builderpages:plasmo:spx-mpu:mpuconn|connector]] definitions
  
 Photo [[:builderpages:plasmo:spx-mpu:mpu302photos|gallery]] Photo [[:builderpages:plasmo:spx-mpu:mpu302photos|gallery]]
builderpages/plasmo/spx-mpu.1502040556.txt.gz · Last modified: 2017/08/06 13:29 by plasmo
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