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Text File | 1993-06-08 | 9.3 KB | 199 lines

This is written for and to anyone who happens to have an Epson Px-8 (Geneva) portable computer and who has not yet been able to make it useful. Part of your problem may be that you are trying to use software that comes with the machine, e.g. "portable Wordstar" or that you are trying to read software in from tape each time prior to execution. In either case, one would recommend that you burn useful software, available for free on this and other bulletin boards, onto rom chips. The rom chip type to use is the 27c256, made by several manufacturers. Eli Heffron / Solid State Sales -- Hampshire Street in Cambridge. Or order from the West Coast discounters, JDR Microdevices, etc. Try to get 200 nanosecond chips if you can. I do not know how fast the chips in fact have to be to work satisfactorily with the machine. I do know that 200 ns works great. 300 probably works as well. Beyond that I don't know. The "c" (for Cmos) is very important. These draw less power than the normal Eprom. You will get just under 32k of files on a 27c256 chip, the precise amount depends upon the number of files and how you can fit them together. (The rom slot in the expansion "wedge" will take a 27512 as well as a 27256. I believe, as well, that two 27c256 chips can be combined in the two carriers for a not quite 64k disk.) You may have to erase the chips. Done using ultraviolet light. Borrow an eraser. Or build one: You will need a small germicidal UV bulb (G8T5 is plenty big), which you can get from one of the big electric supply houses, (Standard, Mass Gas & Electric, etc.) for about $20, and a fixture with a starter and ballast, $11 at Grainger's now in Brighton, or $20 as an "under counter fixture" at one of the electrical supply. Wire and a darkroom timer and you are there. Ten minutes will do most roms. Fifteen is sure. Do not look at the light! Best: put the light in a box that closes. You will need to borrow or build a rom burner, or get a nice person to do it for you. (If you ship me the software and rom chip I will be glad to.) Build: $95 from B&C Microsystems in the back of BYTE mag. The only "trick" to the job is in structuring the directory so that the PX-8 operating system understands it. FIRST IMPORTANT PRINCIPLE: The high order address line is inverted to the rom chip. Thus location 4000 hex is location 0000 hex, and vice versa. The directory, which begins at the beginning of the chip, is thus at what any normal person would call location 4000 hex. SECOND IMPORTANT PRINCIPLE: The 'files' begin immediately after the directory. If the last byte of the directory is at 404F hex, then the first byte of the first file is at 4050 hex. If you have those two - everything else follows. Some PX-8 rom directories from Epson produced roms are listed below: 3FF0 FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF ................ 4000 E537 200F FF48 3830 4241 5349 4320 2020 .7 ..H80BASIC 4010 2020 2020 2020 0456 3130 3039 3136 3833 .V10091683 4020 0042 4153 4943 2020 2043 4F4D 0000 0080 .BASIC COM.... 4030 0102 0304 0506 0708 090A 0B0C 0D0E 0F10 ................ 4040 0042 4153 4943 2020 2043 4F4D 0100 0078 .BASIC COM...x Checksum for the rom is: A7CC 4000 E537 203C 6948 3830 4D32 3530 3436 4341 .7 <iH80M25046CA 4010 2020 2020 2020 0856 3133 3132 3130 3833 .V13121083 4020 0050 4950 2020 2020 2043 4F4D 0000 003A .PIP COM...: 4030 0102 0304 0506 0708 0000 0000 0000 0000 ................ 4040 0053 5441 5420 2020 2043 4F4D 0000 0029 .STAT COM...) 4050 090A 0B0C 0D0E 0000 0000 0000 0000 0000 ................ 4060 0053 5542 4D49 5420 2043 4F4D 0000 000A .SUBMIT COM.... 4070 0F10 0000 0000 0000 0000 0000 0000 0000 ................ 4080 0058 5355 4220 2020 2043 4F4D 0000 0006 .XSUB COM.... 4090 1100 0000 0000 0000 0000 0000 0000 0000 ................ 40A0 0046 494C 494E 4B20 2043 4F4D 0000 0016 .FILINK COM.... 40B0 1213 1400 0000 0000 0000 0000 0000 0000 ................ 40C0 0054 4552 4D20 2020 2043 4F4D 0000 0018 .TERM COM.... 40D0 1516 1700 0000 0000 0000 0000 0000 0000 ................ 40E0 0043 4F4E 4649 4720 2043 4F4D 0000 0040 .CONFIG COM...@ 40F0 1819 1A1B 1C1D 1E1F 0000 0000 0000 0000 ................ 4100 C3CE 04C3 0A01 C31A 011A 2A01 0011 4500 ..........*...E. 4110 1911 1601 D5E9 3209 01C9 2A01 0011 4800 ......2...*...H. 4120 19E9 4E50 3A2F 4F55 543A 5350 4143 4529 ..NP:/OUT:SPACE) Checksum for the rom is: 8600 3FF0 0000 0000 0000 001F 1010 1010 1010 1041 ...............A 4000 E537 20AE 6448 3830 4D32 3530 3432 4341 .7 .dH80M25042CA 4010 454E 474C 4953 0456 3130 3031 3037 3834 ENGLIS.V10010784 4020 0057 5320 2020 2020 2043 4F4D 0000 0080 .WS COM.... 4030 0102 0304 0506 0708 090A 0B0C 0D0E 0F10 ................ 4040 0057 5320 2020 2020 2043 4F4D 0100 004F .WS COM...O 4050 1112 1314 1516 1718 191A 0000 0000 0000 ................ 4060 0057 534D 5347 5320 204F 5652 0000 0029 .WSMSGS OVR...) 4070 1B1C 1D1E 1F20 0000 0000 0000 0000 0000 ..... .......... 4080 C398 0DC3 8F0D C332 2700 0000 4A00 4A00 .......2'...J.J. 4090 0100 0000 0000 0020 2043 4F50 5952 4947 ....... COPYRIG 40A0 4854 2028 4329 2031 3938 3320 204D 6963 HT (C) 1983 Mic 40B0 726F 5072 6F20 496E 7465 726E 6174 696F roPro Internatio Checksum for the rom is: 7822 Checksums, by the way, appear NOT to matter. Unlike PC bios roms. Here below is a sample of a user burned rom: 4000 E537 203C 69FF FFFF FFFF FFFF FFFF FFFF .7 <i........... 4010 FFFF FFFF FFFF 06FF FFFF FFFF FFFF FFFF ................ 4020 0056 4420 2020 2020 2043 4F4D 0000 0079 .VD COM...y 4030 1112 1314 1516 1718 191A 1B1C 1D1E 1F20 ............... 4040 0044 2020 2020 2020 2043 4F4D 0000 0008 .D COM.... 4050 1000 0000 0000 0000 0000 0000 0000 0000 ................ 4060 0054 4552 4D20 2020 2043 4F4D 0000 0018 .TERM COM.... 4070 0102 0300 0000 0000 0000 0000 0000 0000 ................ 4080 0043 4F4E 4649 4720 2043 4F4D 0000 0040 .CONFIG COM...@ 4090 0405 0607 0809 0A0B 0000 0000 0000 0000 ................ 40A0 0056 4420 2020 2020 2051 5246 0000 0020 .VD QRF... 40B0 0C0D 0E0F 0000 0000 0000 0000 0000 0000 ................ 40C0 31C7 0FAF 0100 0821 FE0C CD5B 0236 0A3C 1......!...[.6.< Some principles and features: 1. If we don't know what to do with a particular byte we leave it unprogrammed, i.e. at FF. 2. Number of directory entries is at 4016. 3. Number of 128 byte records in the file is at byte F of the first line of the directory entry. 4. At byte 10 and following of the directory entry is a list of the blocks occupied by the file. Blocks are eight records long, i.e. 1k or 1024 bytes. Blocks are numbered with 01 beginning immediately after the directory. 5. Every succeeding block begins at that same boundary. If block 01 goes from 40C0 to 44BF, block 02 goes from 44C0 to 48BF, etc. 6. There can be a final block which is small in size. It will be a maximum of 1k minus the size of the directory. It still has to end on an even record boundary. See the file VD.COM above. 7. If you need more than the 16 blocks you can list on the second line of an entry, an extension entry may be created by placing a 01 in byte C of the first line of entry. See the WS.COM example above. Finally, you may be wondering whether you need the plastic chip carriers that the roms you got from Epson were mounted in. Those are made by Molex and others and can be bought, with some difficulty, from JDR etc. However, you can, as an alternative, cut a piece of 1/8th inch plexigalss the exact width of the rom chip, bend the rom leads in a rectangular fashion around it, squeeze the chip into the carrier socket so that the leads line up, and it will be there through even a small earthquake. Not quite as easy to change chips, although not that hard, and you will have to distinguish one end from the other -- but a workable answer. Good luck.