I'm reading Zilog eZ80 CPU User Manual at the moment.
Inside, I read that several instructions (like OTDRX, OTI2R...) either aren't supported or operate differently on eZ80190.
Looking for eZ80190, I found in "eZ80190 Product Brief" (
http://www.zilog.com/manage_directlink.php?filepath=docs/ez80/pb0052&extn=.pdf ) , page 5, that there are also eZ80L92, eZ80F91, eZ80F92, eZ80F93...
I wonder "which eZ80 precisely is inside our TI84plusCE / TI83PremiumCE ?"
I think the I/O instructions are disabled on the 84/83+CE because all the I/O is memory-mapped, so it isn 't necessary. (I know it doesn't really answer your question, sorry.)
Turns out I've actually already answered this on TI-Planet, but basically:
- The CPU manual says "The 16-bit I register is not supported on eZ80190, eZ80L92, or eZ80F92/F93 devices."
- We do have/use this register on the CE.
- Thus we apparently have an eZ80F91 (eZ80191?)
An eZ80F91 ?..Thanks !
Hactar wrote:
I think the I/O instructions are disabled on the 84/83+CE because all the I/O is memory-mapped, so it isn 't necessary. (I know it doesn't really answer your question, sorry.)
The I/O instructions are not disabled. If you're in privileged mode (that is, you're the OS), there are ways to use in and out, but the calculator will reset if non-OS code tries to use them.
KermMartian wrote:
Hactar wrote:
I think the I/O instructions are disabled on the 84/83+CE because all the I/O is memory-mapped, so it isn 't necessary. (I know it doesn't really answer your question, sorry.)
The I/O instructions are not disabled. If you're in privileged mode (that is, you're the OS), there are ways to use in and out, but the calculator will reset if non-OS code tries to use them.
Ah, okay. Is there any use for the I/O instructions?
Hactar wrote:
Ah, okay. Is there any use for the I/O instructions?
Yes, you can write to ports with a lot more control than you would be able to with the MMIO instructions. That's about it. Plus you can use them to write to the control port.
Also, it is slightly incorrect that code must be a OS privileged. But that's the general idea.
MateoConLechuga wrote:
Also, it is slightly incorrect that code must be a OS privileged. But that's the general idea.
I figured the high-level explanation without the details of what "privileged" actually means in this context would be most helpful as a first-pass explanation. To be honest, I've forgotten if code in the first sector, boot code, or code with Flash unlocked is what is required to use the ports on these calculators.
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