I was busy with my c64 cartridge project
IRQHack64 lately so I haven't got the chance to contribute to the forum.
I started fresh with a new cartridge project for Atari 2600. I intend to create a cartridge that plays games from a sd card. I'm using a STM32 arm chip.
This is just an introduction but I have 6502 questions related to the atari 2600 hardware.
Atari 2600 have a 6507 chip which mainly has reduced address space and doesn't have interrupts.
As seen from the schematics the console doesn't even have a reset hardware, all that there is just a parallel capacitor with a resistor.
First question : How come this thing got a reset on cpu?
My challenge is : Boot code by emulating an eprom by a stm microprocessor. If that micro boots after 6507 has been reset than there is no means to reset the cpu by the cartridge port. Cartridge port only have address lines (A0..A12) and databus (D0..D7) brought. A12 is used to tell cpu need to access rom on the cartridge. No R/W lines.
Second question : Cartridge port doesn't have a R/W signal. Some cartridges have extra memory on them which are accessed through read and write ports which I guess the original equipment used address decoding to produce the R/W signal. Now the actual question is : With a pure rom cartridge, wouldn't a write access from cpu fight the bus with the rom (eprom or whatever) trying to drive the bus with the contents of the memory? Isn't that a problem?