04-06-2021, 05:07 PM
Had a play with an early Microbee Eprom Programmer today, borrowed from kimjohn, thanks for the lend. It needs a 50way to plug the cable into and the only unit I had handy to have that was my 56k Microbee. No power needed as it gets it via the 50way.
Reading the manual from the Repository (eprom_programmer_and_64k_rom_pak_instruction_manual.pdf), it talks about the default address of the unit being C000h and an inside switch can be used to set to different addresses. Opened it up and there was no Switch 4. Checked the 2 schematics we have in the repository, 8325_3_01 and 8325_4_01. This unit turned out to have an earlier 8325_2_01 pcb. Put it back together and realized later I didnt take a picture of it, oh well.
Plugged the Programmer in and turned on the Microbee. With no drives attached, the bee goes straight to the Monitor, great as thats where I needed to be anyway. Put a spare BN60 2764 eprom in the Programmers socket, switch 1 in down position (for 2764), switch 2 to ROM and turned it on, no sound, no light, nothing happened. Then in the Monitor I used the E command to Examine memory locations to see if I could find the BN60. Sure enough, I eventually found it starting at 8000h, great. I then tried to see if I could read the rom by moving the code to another memory address. I used
M 8000 4000 2000
that Moves the contents of memory starting at 8000h (where the BN60 is) to 4000h and move 2000h bytes (8kb). Red LED comes on and took a couple of minutes. Then using E again, sure enough the BN60 rom code is now also at 4000h. So it can read a eprom but can it burn a eprom?
Without going to the trouble of importing code into the bee I decided to simple try and burn the 4k BN54 (56k boot rom) that was in the Microbee to a 2732 eprom. Put a blank 2732 in the socket, flipped switch 1 up (for 2732) and turned the Programmer on. Checked address 8000h and sure enough was full of FF's. So then used
M E000 8000 1000
that moves the contents of the BN54 in the bee that resides at E000h to 8000h which is where the blank 2732 resides and move 1000h bytes (4kb). The red LED comes on and took 3-4 minutes to turn off. Checked the contents at 8000h and now appears to be the BN54 code. Fantastic looks like its can burn eproms also. I turned everything off, removed the original BN54 out of the Microbee and replaced with the newly burnt eprom and turned the Microbee on, bingo, goes straight to the Monitor as expected.
Not a bad little unit, slow compared to modern units but easy to use and restricted to the eproms used in the early Microbees. I didnt try the 2532 eprom burning or reading either nor see if it could handle a 2716 as used for the early 2khz bee Character Rom. This unit would not be suitable to attach to a ROM based bee, as the default address is 8000h which is were the BASIC rom resides, unless somehow the default address can be changed.
Reading the manual from the Repository (eprom_programmer_and_64k_rom_pak_instruction_manual.pdf), it talks about the default address of the unit being C000h and an inside switch can be used to set to different addresses. Opened it up and there was no Switch 4. Checked the 2 schematics we have in the repository, 8325_3_01 and 8325_4_01. This unit turned out to have an earlier 8325_2_01 pcb. Put it back together and realized later I didnt take a picture of it, oh well.
Plugged the Programmer in and turned on the Microbee. With no drives attached, the bee goes straight to the Monitor, great as thats where I needed to be anyway. Put a spare BN60 2764 eprom in the Programmers socket, switch 1 in down position (for 2764), switch 2 to ROM and turned it on, no sound, no light, nothing happened. Then in the Monitor I used the E command to Examine memory locations to see if I could find the BN60. Sure enough, I eventually found it starting at 8000h, great. I then tried to see if I could read the rom by moving the code to another memory address. I used
M 8000 4000 2000
that Moves the contents of memory starting at 8000h (where the BN60 is) to 4000h and move 2000h bytes (8kb). Red LED comes on and took a couple of minutes. Then using E again, sure enough the BN60 rom code is now also at 4000h. So it can read a eprom but can it burn a eprom?
Without going to the trouble of importing code into the bee I decided to simple try and burn the 4k BN54 (56k boot rom) that was in the Microbee to a 2732 eprom. Put a blank 2732 in the socket, flipped switch 1 up (for 2732) and turned the Programmer on. Checked address 8000h and sure enough was full of FF's. So then used
M E000 8000 1000
that moves the contents of the BN54 in the bee that resides at E000h to 8000h which is where the blank 2732 resides and move 1000h bytes (4kb). The red LED comes on and took 3-4 minutes to turn off. Checked the contents at 8000h and now appears to be the BN54 code. Fantastic looks like its can burn eproms also. I turned everything off, removed the original BN54 out of the Microbee and replaced with the newly burnt eprom and turned the Microbee on, bingo, goes straight to the Monitor as expected.
Not a bad little unit, slow compared to modern units but easy to use and restricted to the eproms used in the early Microbees. I didnt try the 2532 eprom burning or reading either nor see if it could handle a 2716 as used for the early 2khz bee Character Rom. This unit would not be suitable to attach to a ROM based bee, as the default address is 8000h which is were the BASIC rom resides, unless somehow the default address can be changed.
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ChickenMan
ChickenMan