FORTH for the SHARP PC-E500 (S)

[robve]

(11-07-2021 05:44 PM)Klaus Overhage Wrote:  UULOAD.BAS from the same archive seems to be an implementation in BASIC of the way you suggested: It reads in a UUE file via the COM interface, checks whether the first 16 bytes are as requested by LOADM and writes the bytes directly into the upper RAM. I tried it with FORTH500.UUE: It only worked 10% after 4 minutes, so I canceled it.

BASIC decoding is too slow to keep pace with the serial interface.

The UUDECODE.ASM implementation isn't complicated and the code is actually a bit convoluted. It has a lot of unnecessary extras that can be removed. Since we only want to read the uu file from COM:, the code that parses the argument passed to the decoder as a CALL argument can be removed. The file to create and write is not needed when saving the decoded data directly to memory. The display messaging, error reporting and uu file header parsing can be removed to significantly reduce the code size to a bare minimum. I played a bit with this to "trim the fat" by removing all non-essential parts and got the machine code down to 453 bytes. To bootload this code via BASIC with POKEs in hex will be more than 1K, a tad too large if 950 bytes of BASIC are available when space is allocated for Forth500 unless we move Forth500 up in memory by one or more page sizes (multiples of 256 bytes). With only 400 bytes or so remaining, rewriting UUDECODE.ASM appears an option, BUT... I cannot try it out to test it. Unfortunately, my CE-134T doesn't work with low RS232 USB dongle voltage levels. I'm glad to have received suggestions to DIY a serial interface, but I'm concerned with overvoltage levels or ESD damaging the E500.

- Rob