• Please review our updated Terms and Rules here

Booting TRS 80 Model 4 from RS 232

GravityCrab

Member
Joined
Jan 16, 2015
Messages
48
Location
Gainesville Florida
Is it even remotely possible to load LDOS or TRSDOS from the parallel port on the bottom of this computer or am i completely in the realm of fantasy over here?

- David
 
The title says RS232, but the body says parallel port. In which are you interested?

There used to be a site describing a Model 4P serial bootloader. The link is on Tim Mann's site. But the bootloader is no longer listed on it. Might be archived somewhere.

I don't think the parallel port is bidirectional, but I could be wrong.
 
There used to be a site describing a Model 4P serial bootloader. The link is on Tim Mann's site. But the bootloader is no longer listed on it. Might be archived somewhere.

There's a DOS program that will download a boot program over RS-232 to a 4P: http://www.hytherion.com/beattidp/comput/sboot4t.htm

The source code pretty well describes the protocol, as I recall. There's a little back-and-forth so that the 4P can auto-detect the baud rate and then you pretty much just send something in "/CMD" format. On the 4P side you need to hold down on SHIFT and BREAK to put it into "RS-232 boot" mode.

I've written my own downloader for windows but haven't gotten around to making it publicly available. It's not terribly useful unless you want to run standalone programs on the machine.

While the 4P does have this RS-232 boot feature, there isn't a version of TRS-DOS or LDOS that will boot over the serial line.
 
Is it even remotely possible to load LDOS or TRSDOS from the parallel port on the bottom of this computer or am i completely in the realm of fantasy over here?
The Model III/4 parallel port has 8 lines in each direction, plus a strobe output.

It's certainly possible to (1) design a protocol for receiving input through the parallel port; (2) build a device that attaches to the parallel port and sends DOS through the port using the protocol; and (3) install a custom ROM with code to use the protocol to load DOS from that device through the parallel port. As with FreHD, you could probably make the protocol simple enough, and the Z-80 code to implement it compact enough, that you could fit it in the ROM along with all of BASIC except the low-speed cassette routines.
 
Back
Top