Tandy TRS-80 model 4p

Under construction.
Front TRS-80 model 4p Keys at reset:
.             Run RAM test
V             Print boot ROM version
1, F1         Hard Disk boot
2, F2         Floppy Disk boot
3, F3         Model III boot
RIGHT-SHIFT   RS-232 boot
P             Prompt disk switch at ROM-image load
N             Ignore OS request for ROM-image load
L             Force reload ROM-image
BREAK         Set flag at 405BH
ENTER         Terminate keyboard routine
LEFT-SHIFT    Reserved
CTRL          Reserved
CAPS          Reserved
Semi side TRS-80 model 4p semi side view

The solution

chromedome's IDE interface

Chromedome created an interface that actually works. See Cheapo-IDE-interface-for-Model-4p-running-MM-CP-M for more info on this interface.

First version of my TRS-IDE interface

TRS-IDE prototype

TRS-IDE prototype

TRS-IDE with disk

Remember to reorient the IDE connector on the next board

Entered the following BASIC program (with a disk connected):

10 AD=63
20 X=10
30 OUT 236,16
40 FOR Y= 0 TO X
50 PRINT Y+AD;" ";INP(Y+AD)
60 NEXT Y

The result was:

63 255
64 0
65 1
66 1
67 1
68 0
69 0
70 80
71 80
72 1

The Seagate (ST3144A) doesn't work. Currently testing with a Conner (CP3008E).

Enter:

 SYSTEM (DRIVE=2, DRIVER="HDDVR6")

TRSIDE - IDE Disk Driver for LDOS 6.x/5.x
Enter drive select address <1-4>: 1
Enter total number of heads on drive <1-8>: 8
Enter physical tracks per surface: 22
Heads already in use <.-.-.-.-.-.-.-.>
Enter number of heads for partition <1-8>: 2
Enter starting head: 1

Now a blinking "H" should appear in the upper right side of the screen.

With some drives it does, but the drive is not addressed.

External IDE for 8-bit bus designs


Last update: 2015-03-03

fjkraan@electrickery.nl