Anyone have a schematic for a DSR board?

[+jedimatt42]

I have a basic subroutine 'CALL' embedded in a DSR, that find the first program record in the Cartridge program chain and jumps there.

 

So, I've tested in Classic99, with this DSR loaded: cart_DSR.bin

 

configured like:

 

; EA IV

name="Editor Assembler IV"

rom0=3|0000|8000|MODS\EAIV\eaprom_IV_INV.bin

rom1=D|4000|1000|MODS\gcc_DSR.bin

 

That with the QI/v2.2 TI, I can go into basic and enter: CALL CART

And it will take me into the ROM cart..

 

This is cool. Cause I have a v2.2 beige console, I want to use my memory board and a all these new ROM cartridges with... So I'd like to put this in an eprom and wire it to that little expansion port on my sideport 32k device.

 

I imagine there are ways I could do this wrong, just use the >4000 signal on the sideport to control enabling the rom, and data buffer. But I imagine it should respect only being in when a CRU port is set... Does anyone have a starter circuit for doing this?

 

My DSR is just these two little snippets..

header.asm

# ROM header  
  byte 0xAA, 0x00, 0x00, 0x00

# Start of power-up chain (unused)
  data 0x0000
# Start of program chain (unused)
  data 0x0000
# Start of DSR chain (unused)
  data 0x0000
# Start of subprogram list
  data callgame
# This doubles as the terminator of the program chain

callgame:
  data  0x0000    
# Next program chain record
  data  _start    
# Entry point for program
  nstring "CART"
# Name of program  even

and

 

def _start

_start:
  limi 0       # Disable interrupts
  lwpi >8300   # Set initial workspace
  mov @>6004,r1
  ai r1,2  blwp r1

I suppose I should actually check if >6000 contains the requisite >AA header byte.

 

( I know all of this has done before BITD... and more recently there is a playground solution... I'm just aiming to make this easier. )

 

-M@

Edited October 1, 2016 by jedimatt42

[sometimes99er]

Very nice.

 

Regarding v2.2, you could just replace GROM 0.

 

And for any version, you can skip the TI title-screen and go directly into the cart. Nice, though I kinda like to have title and selection.

 

[Stuart]

If you look at Thierry's page for the Horizon Ramdisk [http://www.nouspikel.com/ti99/titechpages.htm] that shows the schematic for the DSR RAM as well as the ramdisk RAM. Should give you a place to start, although you should be able to simplify things considerably. Looks like you'll need something like:

 

-- 74LS138 to decode the CRU address for your 'card'.

-- 74LS259 to latch a 'card enabled/disabled' CRU bit.

-- Your EPROM.

-- 74LS245 data buffer.

-- Miscellaneous logic gates and other components.

[+jedimatt42]

Very nice.Regarding v2.2, you could just replace GROM 0.And for any version, you can skip the TI title-screen and go directly into the cart. Nice, though I kinda like to have title and selection.

My entire premise is to learn how to handle the CRU selection.

 

My secondary goals are:

* No modifications to a v2.2 console

* Enable running carts with multiple program entries.

* Does not interfere with existing hardware

* Can be left connected 24/7

* No switches required during use.

 

I plan to expand the routine to go to a menu if there is more than one entry.

 

-M@

[+jedimatt42]

And Stuart,

 

Thanks! The ramdisk write up is clearer to me than his general cru selection circuit.

 

-M@

[Stuart]

Matt, have you got a copy of the "Interface Standard & Design Guide for TI-99/4A Peripherals" book by Tony Lewis? That covers DSRs and has some circuit bits as well - you'd probably find it interesting. Not sure where you got a copy from though - I believe it's still available so probably no scanned copies around. Someone else may chip in if they know where you can get a copy from.

 

Stuart.

[+jedimatt42]

Matt, have you got a copy of the "Interface Standard & Design Guide for TI-99/4A Peripherals" book by Tony Lewis? That covers DSRs and has some circuit bits as well - you'd probably find it interesting. Not sure where you got a copy from though - I believe it's still available so probably no scanned copies around. Someone else may chip in if they know where you can get a copy from.

 

Stuart.

 

No, I don't have that. Sounds like exactly what I need to absorb. Anyone want to sell me one?

 

http://www.whtech.com/ti/guide.html

 

-M@

Edited September 30, 2016 by jedimatt42