PPU double read/write registers

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Kaisha
Posts: 14
Joined: Mon Apr 26, 2021 2:58 am

PPU double read/write registers

Post by Kaisha »

A number of the PPU registers are double read/write, in that we read/write to the same address twice the low then high byte of a 16-bit value. So obviously under the hood there must be some flag (or internal state) set to indicate when a low byte read/write occurs, and when the high byte is read/written.

Is this internal 'flag' shared by all double registers? If I were to say only write 1 byte to 0x210D and then 1 byte to 0x210E what would happen? Does a read/write to another register cause a reset?
lidnariq
Posts: 11432
Joined: Sun Apr 13, 2008 11:12 am

Re: PPU double read/write registers

Post by lidnariq »

I was going to write a long post with cites, but I think it's more useful if I just link to this old thread: viewtopic.php?t=16200
Kaisha
Posts: 14
Joined: Mon Apr 26, 2021 2:58 am

Re: PPU double read/write registers

Post by Kaisha »

Thank-you :)
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