FarmerPotato

For detecting address >7fff you might use a 74LS133 13-input NAND gate to gather all 13 address lines. It's obsolete but $0.49 at Unicorn Electronics Except, be aware the 9900 reads 16 bits at a time, so it always reads 7fff then 7ffe. (and then maybe writes.) Also if you're not already friends with the '138, or even if you are, the '138 can match 3 address inputs A,B,C and has 3 chip enables (G2A*,G2B* low, G1 high.) (There are several of these inside the 4A.) When the enables are matched, the A,B,C inputs determine which one of the outputs=0. Below, BLOCK_7E00 goes to 0 when there is a write anywhere in 7E00-7FFF. Etc. You can decode memory writes to smaller blocks by cascading them: Here, the second '138 matches on A15=0 and A7=1. The outputs like O7 could connect directly to an LED (base) for pulsing, or drive a flip-flop. Writing to any address in >7FE0 to >7FFF will cause BLOCK_7FE0 to pulse low for a moment. A bigger deal is interfacing a TLC5940 16-LED driver. (all drawings made with KiCad 5)

Here is one way to do it with pullup resistors for the chip that is not in use:

This is the superimpose switch: ________ YS1* ---|Set | Vcc-----|D Q|________ YS2* ---|Reset | ! |________| ! JK flip flop ! _____!__ YS1* ---------------|A sw | | Y|__ !YS2*---------------|B | ! |________| ! analog switch ! ! _____!__ RGB1 --------------------1|\ sw | | > --RGB|------ RGB RGB2 --------------------0|/ | |________| fast RGB switch VDP1 outputs YS1*, RGB1 (R,G,B) VDP2 outputs YS2*, RGB2 (R,G,B) VDP1 and VDP2 are synchronized (not shown) When a superimpose bit is active, YS1* or YS2* emit 0s for transparent pixels. The first one to emit 0, flips Q to its side. If YS1* flips Q to 1 (the default on powerup), the analog switch passes YS1*. If YS2* flips Q to 0, the analog switch passes !YS2*. The fast RGB switch normally passes RGB1. When Q=1 and YS1*=0, it passes RGB2. That is, transparent pixels on VDP1 result in VDP2 showing through. If Q=0, the situation is reversed. The switch passes RGB2, but transparent pixels on VDP2 cause the switch to pass RGB1. This circuit minimizes the parts cost: there is only one expensive (350MHz) RGB switch (AD1675-1 x3). It minimizes skew: VDP1 over VDP2 is the direct path. But VDP2 over VDP1 may have a slight skew from the NOT function of !YS2* which may blur the pixel transition a bit. It's undefined what happens if both VDP1 and VDP2 have the superimpose bit set. They would constantly fight for Q, which is not a fast switcher; neither is Y. The output could be deeply weird. What use cases does this support? 1. VDP2 over VDP1 would let you put titles onto VDP2, then run a normal 99/4A program (that is unaware of the Twin 9958) on VDP1 under the titles. 2. VDP1 over VDP2 would naturally be a way to get another scrolling plane, extra colors or deep background sprites.

I've worked out most of the BOM and schematic for the twin 9958 option. No PCB layout yet. Parts ordered. Features it does include: Superimpose VDP1 over VDP2, or VDP2 over VDP1 on connector 1 only (simply set the Superimpose bit on one VDP, but never both.) Mirror mode at startup Independent VDPs after the first write to VDP2 only 128K VRAM each. RGBs, CV, SV out (Sony CXA2075 composite/SV encoder) NTSC/PAL jumper Choice of any 1 or 2 monitor jacks (twin 6x2 ribbon cables from board to jack PCB) Single 9958 is an option by removing half the circuit. Does NOT include: External video input Extra 64K expansion VRAM Fitting inside the console... maybe, maybe not. Uses 2x20 footprint to the 9918A socket plus 2 jumpers. I'm planning ribbon cable to external. Convenient kit form.. uses surface mount but no smaller than 1206, 1.27mm, 1.78mm. I decided against AD1675-3 in 0.6mm TSSOP. The 1.27mm costs more $. BUT this went down a priority level when my FORTI-2 PCB arrived. Too many projects! I am also a big fan of the F18A and mk2. I anticipate making only about 10 of these Twin 9958.

Do bring your Atari 2600! That gave me an idea. Do you have any ideas for a Parsec 2? There were some insightful comments by matthew180 about Parsec's shortcomings on "least favorite game". We have F18A (matthew180's creation) and I'm mindful there was never a showcase game for the Geneve (9938 video chip). So much greater graphics capabilities could be used (full screen scrolling... larger sprites..) That's as far as I've imagined it.

Sorry, I forgot Game Over was in other cities and that you were in N.B.! The store(s?) in Austin sponsor Classic Game Fest on Jul 28. Leaflet could have the important details (from top of this thread) and some photos of TI gear/screens. You can put your Parsec 2600 in it! You could offer them an ad space in the leaflet. Do what you think will make them feel good! I can pay for color printing at Fedex or wherever.

That's great! About talking to the Game Over manager. (Which store? I found an E/A cart at the one on Anderson Ln.) Do you want to work on a postcard or leaflet? I wonder if we can get some postcards into Classic Game Fest? (BTW I contacted the guy who is demoing the TI version of IRATA.online at CGF.) I'm still working on a vector art Texas License Plate "99/4ATX" logo in CorelDraw (A GIF is in lo-res on the Facebook event).

I had success with the new XGecuPro, programming the AT29F040 EEPROM in the PLCC32 adaptor, and the ATF22LV10C programmable logic in the PLCC28 adaptor. These are my new working set of chips! (Thanks Jim!) I had a scare when the first 22V10 was not detected. The internet says these are difficult to program. Three of my input pins were bent towards a GND pin by my inept first-time use of the removal tool. The next chip succeeded! I tested and verified the 22V10 combinatorial logic at 3.3V. I'm posting because other AtariAge users had a lot of difficulty getting these programmed. I spent $10 making this adaptor , just what I needed for testing.

Return to Pirate's Isle is in good shape, it would be a shame to recycle that one.

How about a Sat afternoon slot? Up to you. There is a gigantic LCD screen to share. There is usually a projector. With a proper screen. (I think the lamp EOLed, I'll ask if its back.) If you need any hardware continuously, like a TV or composite monitor for regular TI output, or a VGA/DVI/HDMI monitor, request that on the Google Doc.

I made a schedule as a shared Google doc. You can add what you're bringing and schedule a demo time. Or you can wait to pick a demo time when you show up, or not even pick a time. The event comes together from what people want to share. Most of the weekend is unstructured time. Scheduled demos should be from 15 to 40 minutes, and you can choose to broadcast it or not (for online viewers). You can announce on this thread what you're bringing. We have the classroom for main activities, but the lobby is another place for displays, and there is a lounge/kitchen. Links Schedule: https://docs.google.com/spreadsheets/d/17e-KIgN7mM-ein3EAs2fQ4A5MTpYuQbS7AzJJElFghw/edit?usp=sharing Facebook event in TI-99ers: https://www.facebook.com/events/683664975426741/

I created a Facebook event in TI-99ers Tell your friends! https://www.facebook.com/events/683664975426741/

This must be a Lost Pyramid of the Inca, because it's a model of the Temple of Inscriptions, Palenque, deep in Maya territory.

Aha, there is a footnote to ABS. "Operand is compared to zero for status bit." Not the result. So, the status tells you about prior to ABS. I would expect ABS R1 JLT HERE to jump if the sign had been -1 before ABS. I've never known or knowingly relied on this.

9900 Family Systems Design p 8-132 says Single Operand Instructions that compare results to zero are: INV, NEG, INC, INCT, DEC, DECT These do NOT compare results to zero: B, BL, BLWP, CLR, SETO, ABS, SWPB, X So, either SETO or ABS leave the jump undetermined.

I populated the 2nd prototype PCB of FORTI-2 a week ago. I have not made a thread for that yet.

I'm taking your cue and using a USB battery pack to power the TiPi or nanoPEB. For the Pi itself, I use a trusted iPad 1.5A power cable. (eevblog did a teardown showing the isolation in Apple's phone charger, vs the lack of isolation in a clone.)

This is not exactly a gadget, but, it's in my toolbox now. I found this new tool for circuit simulation on iPhone: EveryCircuit. I was away from my computer and had a burning desire to do SPICE. It is a totally candy-coated SPICE simulator, but, I'm not complaining. Here are some screenshots of a driver with capacitive coupling. The circuit mocks up (badly) a video output of the V9958, in the range 2V-3V, being coupled to a next-stage (anything: encoder, amplifier, switch) requiring 1V peak to peak input. The app lets you play with all the parameters in real-time.

On the other hand, MBX Baseball was pretty good. Still not as much joy as Intellivision Baseball, the only great sports game on that system. Atari 2600 Basketball was ok. That much could have been viable on the TI-99/4A. For whats its worth, Indoor Soccer and Football were produced in the earliest days of the 99/4.

Got it. I found the analysis of V9938 memory timing by Wouter Vermaelen. Using a logic analyzer, he finds the number of potential slots (per display line) for the CPU or the command engine to access DRAM. By mode, these are: Sprites on: 31 Sprites off: 88 Display off: 154 (or during vertical interval) He goes on to state that with sprites on, the command engine is limited by available memory bandwidth, but with sprites off, it is not 2x faster so therefore limited by itself.

To put it in context, I was playing marathon sessions of The Attack when the coolest game on the block was Atari 2600 Space Invaders. Sure, it was dog slow, but to this 9 year old it was scary.

Oops.. I did not realize TF was a cartridge. I am a plain TI FORTH guy still (but owns a fbFORTH cartridge) You put tape over or cut trace #1 http://www.unige.ch/medecine/nouspikel/ti99/pinouts.htm#Cartridge Mini Memory has another interesting feature where the GROM READY finger is shorter than the others. I don't know why.