2024 Advanced PCB Remake For The 800XL -- Revision 1.2

[reifsnyderb]

I've been making changes to Revision 1.1 and now have Revision 1.2 almost ready.

 

Link to thread regarding Revision 1.1:  https://forums.atariage.com/topic/357302-2023-advanced-pcb-remake-for-the-800xl-revision-11/

 

 

This remake has all the improvements as included in Revision 1.1 as follows:

 

1. Chroma video output on monitor port pin 5.

2. +5VDC on PBI pins 47 and 48.

3. /HALT on PBI pin 33.

4. The optional blur capacitor (C56, 180pF) was re-added.

5. An enhanced MMU with the following changes:

  a. Open collector PBI Refresh to prevent ANTIC’s Refresh signal from being shorted out due to the actions of some PBI upgrades.

  b. PBI RAM at $D600-$D7FF. (Inspired by Atari’s original XL Sweet 16 design document.)

  c. ROM access on read only.

6. Improved DB-9 joystick ports.

7. Full copper ground planes on both sides.

8. Isolated audio and isolated video ground planes.

9. Reduced the component count by making the following changes:

  a. Replaced all DRAM circuits with SRAM circuits.

  b. Replaced the OS and BASIC ROMs with a single chip.

  c. Combine the functions of the 74LS138 and memory control into a single PLC.

  d. Eliminate the ferrite beads and unnecessary 1nF capacitors.

  e. Simplify the power circuitry.

  f. Replace many resistors with resistor arrays and networks.

  g. Replace the audio circuit with the audio circuit designed by mytek on the AtariAge forums.

  h. Remove the RF video in favor of composite and S-Video.

  i. Use the simplified clock circuit used by mytek on the AtariAge forums.

10. Multiple memory options that include 64k only, 128k XE, and 320k RAMBO.

11. Addition of the jumpers as per Atari’s original XL Sweet 16 design document. (These are optional.)

12. Addition of three breadboard regions for user customization.

13. Channel select switch has been re-purposed as a ROM bank select switch to permit two possible OS/BASIC configurations.

14. Addition of separate pads for console keys.

15. Most components have values and/or part numbers on the board to aid in assembly and troubleshooting.

16. Addition of a fuse and zener diode to protect against power supplies going over- voltage. (This is experimental.)

 

Included are some new changes for Revision 1.2:

 

1.  Add an option to enable MapRAM.  (Permits access to 2k of RAM that is located in the Device I/O region from $D000-$D7FF.)

2.  A breadboard style connection region was added to the left of the SIO port to assist when adding internal SIO upgrades such as the S-Drive simple.
3.  Minor video trace improvements were made.
4.  Composite video only components are now labelled.
5.  Add +5v and GND inputs are now shown on the board in the event a different power connector is to be used.
6.  Improved power routing to cartridge port by proper electrical location of the associated 100nF capacitor.
7.  Added optional capacitor footprints for primary oscillator crystal.  This makes it easier to install non-Atari crystals.
8.  Added minor fix for ground lines around Phi2 near PBI.
9.  Most pins on the Atari LSI chips are labelled.

10.  Solder jumpers are added under the ROM chip to support larger ROM sizes in the event the 128k ROM is not available.  (On this board, I am using the 39SF020A as I need to order the smaller ROM and I have some of these collecting dust.)

 

I still have a little more testing to go.  You may notice the occasional component missing as I need to order some more parts.  For example, the 10k ohm resistor array, for the data bus, is missing so the data bus is presently floating.  However, the Atari 400's and 800's had a floating data bus so it's nothing new.  Once I place a parts order, I'll install it.  As expected, it's working with a floating data bus.  I also temporarily jumpered the fuse as I discovered I need to order the fuse contacts.

 

The jumpers do work nicely with the latest OS release as removing the first jumper will start the self test and removing the second jumper will disable the attract mode. 

 

 

PBI region of the board.  Note the extra little bread board/connection region to the left of the SIO connector.

 

Optional capacitor footprints are above and below the crystal.  Not visible, and under the crystal, are the pads to install an OEM crystal.

 

 

PBI RAM and MapRAM jumper options:

 

Most pins are labelled so as to make it easier to install internal upgrades.

 

Board overview:

 

 

 

 

 

 

 

[+mytek]

@reifsnyderb this might be of interest to you.

 

 

EDIT: I later found out that by switching over to an 74HC14, the duty cycle will be 50/50 as it should be, but that the square wave isn't ideal for the GTIA, and you wiil get color offsets. In that particular case I left out the resistor and just used the capacitor across the output, but increased it to 470pF instead.

Edited Thursday at 08:29 PM by mytek

[Mathy]

Hello Brian

 

Maybe you can add a connector for Overange's test/mini keyboard.

 

Sincerely

 

Mathy

 

[reifsnyderb]

2 hours ago, mytek said:

@reifsnyderb this might be of interest to you.

 

 

I just applied your upgrade, as best as possible (I had the resistor but had to put a 100pF and 47pF capacitor in parallel.), on my Rev 1.1 system board.  I can see the difference on the scope but can't find any software to test it with yet.   So, I haven't seen a difference.  I'll keep looking.

 

One difference is that my video circuit is closer to Atari's, but with some changes.  The closest capacitor to your C20 is my C53.

 

 

 

 

Edit:  I just saw your edit to your previous post.  Thanks!

 

 

 

 

 

 

Edited Thursday at 09:26 PM by reifsnyderb

[reifsnyderb]

53 minutes ago, Mathy said:

Hello Brian

 

Maybe you can add a connector for Overange's test/mini keyboard.

 

Sincerely

 

Mathy

 

Link?

 

Is this it?  

 

 

Edited Thursday at 09:21 PM by reifsnyderb

[reifsnyderb]

3 hours ago, mytek said:

@reifsnyderb this might be of interest to you.

 

 

EDIT: I later found out that by switching over to an 74HC14, the duty cycle will be 50/50 as it should be, but that the square wave isn't ideal for the GTIA, and you wiil get color offsets. In that particular case I left out the resistor and just used the capacitor across the output, but increased it to 470pF instead.

 

After a bunch of swapping back and forth, I found something I could use as a "test", of sorts.  On Atari's PacMan cartridge, the "PACMAN" lettering on the first screen at the top should be all yellow.  On the board with the 50/50 duty cycle, all pixells on the left edge of the lettering are white.  On the board with the uneven duty cycle, the lettering is all yellow.  My current theory is that the 2 buffer transistors, in the color circuit, are "fixing" this issue on the uneven duty cycle board.

 

 

 

Edited Thursday at 09:54 PM by reifsnyderb

[Overange]

9 hours ago, reifsnyderb said:

Link?

 

Is this it?  

 

 

This is the pinout J1 is the 24 idc header corresponding to the standard Atari keyboard connector.

it has been integrated into the 600xl remake PCB and works very well,  you have to also install a header to use the mini keyboard.

 

 

[olix]

Yes, the connector for the mini keyboard would be very helpful.

[Mathy]

Hello Brian

 

On 10/3/2024 at 10:40 PM, reifsnyderb said:

Link?

 

Is this it?  

 

 

 

Yes, that's it.

 

Sincerely

 

Mathy

 

 

 

 

 

[Mi1ez]

I love this so much.  Thank you!

[Mi1ez]

On 10/4/2024 at 2:25 AM, Overange said:

This is the pinout J1 is the 24 idc header corresponding to the standard Atari keyboard connector.

it has been integrated into the 600xl remake PCB and works very well,  you have to also install a header to use the mini keyboard.

 

 

Hang on... There's a 600XL remake PCB too??

[olix]

Yes, the 600XL+

It has also 512 K ram extension and a UGV Video Part onboard and Stereo Pokey also. And there is also an extension for a inside FujiNet.