The packet program though not written myself but by a friend of mine, Peter, who was also an active SYMer, was written and compiled using Pascal 5.05 back in the early 90's and uses all the conventional DOS notations. I have modified the program to make it Y2K compliant and also added the ability to abort saves made to the PC if the filename existed. The original program just overwrote the existing file with no questions asked. The ability to save and load third party files became more apparent so writing this program became necessary to allow full usage of the EPROM burner program. This page will explain the usage of the program in more detail. The following commands are available and are also displayed on the bottom of the screen:ALT-L: Load a file from the PC to the SYM.
The top of the screen displays current version and current drive/path information.
When saving a file from the SYM to a PC, the packet program looks for a certain file extension. If the extension is .ROM, the file is saved exactly as in the SYM with no changes made to the binaries whereas if the file is saved as a .BIN or any other extension, the program inserts two bytes at the beginning of the file for later use by the ALT-L - load command. Assume a file exists on the SYM for a 4K EPROM located in memory $2000 to $2FFF and you want to save it. Pressing ALT-S produces the following:
Enter file name ? - Enter any character name (up to eight) followed by any three letter extension and (cr).
Enter start address, end address: - Enter 2000,2FFF (cr). Use only a comma or dash as a delimiter.
The program will either proceed with the save or prompt displaying the message "XXX already exists. Overwrite (Y/Cr=No) ?" where XXX is the filename.
If you wish to overwrite the existing file press Y and (cr) or else (cr) to abort the save.
If the file was saved using a .ROM extension and an ALT-L is performed to load the file back into the SYM, the program will display the default location of <$1000> for the load. The user may then enter any value for the load. Assume this time you want it loaded at location $4000. Just type 4000 and press enter. The program will now load the file to memory hex 4000. The leading dollar sign is not necessary as hex values are always assumed. Now in another example, assume you saved the file as a .BIN from location $5000. Upon entering an ALT-L to load the file back into the SYM, the default location of <$5000> will be displayed, the original save from location. You cannot change this default. The file will be saved at location $5000 EXACTLY as it was saved to the PC originally minus the first two bytes which are only used by the ALT-L program to determine the original "saved from" location. Pressing ALT-L produces the following:
Load filename ? - Enter the filename WITH the extension.
If the file is found the following prompt is displayed "enter start address: <$1000>". Remember that if the file was saved with a .ROM extension the above message will be displayed and you will be able to load the file to any valid memory location whereas if the message displayed is "enter start address: <$4000>, the only possible answer is a carriage return. Even if the original file was saved from $1000 and has any extension other than .ROM, it cannot be relocated by the load command. The rule of thumb would be to save most files with a .ROM extension for later relocation upon retrieval if necessary. You could always exit the program with CTRL-C and use the SYM monitor command to block move the binaries to any valid memory location. Re-enter the EPROM burner at the SYM prompt . with a g (cr). Communication protocols are either 4800 baud, 8 data and 2 stop bits OR 9600 baud, 8 data, and 2 stop bits. Both programs use COM 1 only.