[Coco] DLOAD

[Roger Taylor]

I'm trying to figure out if it's possible to enable the DLOAD comnmand on 
the CoCo 3.  I realize that the ROMs are running from "All-RAM" mode and 
that DLOAD is normally overwritten, but when I switch to ROM mode (POKE 
65502,0) DLOAD still does a warm boot or reset.

Has anybody experimented with this?  I'm going to dig into the ROM source 
tonight and see what's happening.

Also, I've tried DLOAD on two CoCo 2's and neither one will send out over 
the bitbanger port correctly at the 1200bps setting.  300bps works 
great.  Using a serial port monitor on the PC, it shows that no matter what 
cable I use and CoCo I use, sometimes the byte (138) gets received as (10) 
on 2 different PCs, which tells me that there is probably a bug with the 
1200bps setting which is small enough that a start bit and 7 data bits 
makes it ok into the PC but the 8th data bit isn't stable.

Using two PCs (one with a standard COM port and the other with a 
USB-to-serial adaptor), two CoCos, two cables, no matter how I mix and 
match them, I get the same results trying to use DLOAD "FILE",1  the 
1200bps setting.

So, my tests prove that it's the delay value for 1200bps in the DLOAD 
command.  The code (or the Unravalled Series PDF files) shows that the 
delay for 300bps is 44 and the delay for 1200bps is 44*4, but since the 
BASIC printer output code doesn't use constant-scaled delays, I can't see 
why DLOAD can.

The only way I can test this theory is by using a 64k CoCo 2 which has been 
put into the All-RAM mode where the ROMs are copied into RAM and run from 
there, and I can patch the DLOAD code.




-- 
Roger Taylor