Author Topic: WikiTI  (Read 40288 times)

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Offline Xeda112358

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Re: WikiTI
« Reply #90 on: May 13, 2014, 10:00:28 am »
Speaking of the key port...
I don't know if anybody else does this, but in some high-speed programs that only use 1 or 2 groups, I disable interrupts, set the key group(s) I need, and I never have to write to the port again (just read). So for example, I made a Snake game that only used the arrows and [2nd], [mode], and [del], so I wrote $BE to the port. At the beginning of the game loop, I just need to do in a,(1) with no worry about delays to read the key press. So yeah, in some of my games, pressing things like F2 to F5 will also act as arrow presses.

Otherwise, if I need _GetK and the program needs to be small and can use interrupts, turn on interrupts and spend only 13 cycles to either read 8445h or 843Fh (whichever is needed) for the same effect.

Offline Streetwalrus

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Re: WikiTI
« Reply #91 on: May 13, 2014, 10:53:35 am »
Oh wow that's what Soru was talking about the other day. O.O Nice trick.

Offline Sorunome

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Re: WikiTI
« Reply #92 on: May 13, 2014, 11:50:35 am »
Oh wow that's what Soru was talking about the other day. O.O Nice trick.
Hehe, I got the trick from Iambian and geekboy :P

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Offline the_mad_joob

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Re: WikiTI
« Reply #93 on: May 13, 2014, 07:48:28 pm »
Yes xedy, reading multiple groups at the same time should be done, when possible =]

I'm very curious about something.
Like i said earlier, we basically have these 2 behaviours :

write
delay
read

or

reset
delay
write
read

The question is, why doing a reset removes the delay needed bewteen a write & a read ?
Hardware-speaking, i have no ideas how the keyboard really works, but i have a theory that could explain that.
What if :

Case 1 : The writing causes one or more group(s) to be disabled (one or more bit(s) in the group map changes from 0 to 1). > slow operation for the keybord, delay required before reading
That is the case when you switch from one group to another, for example.

Case 2 : All other cases (enabling groups or not modifying them) > very fast operation, no delay
That is the case when you write anything after having performed a reset, but also when you enable some more groups without disabling the previous ones.

I will try to verify that asap...

#####

EDIT 1 :

Ok, just tested it, and it doesn't work like that.
However, i found something strange.
Here is the code i used :
Code: [Select]
    di

    ld a,1
    out ($20),a ; 15Mhz

    ld a,00000010b
    out (1),a ; enabling all groups except the one including [CLEAR]

    ld b,0
loop1
    djnz loop1

loop2

    ld a,11111101b
    out (1),a ; enabling group including [CLEAR]

    in a,(1)
    cp 10111111b ; checking if [CLEAR] being pressed
    jr nz,loop2
As you can see, there is no delay before i read port 1.
Guess what ? PC actually exits the loop instantly when i press [CLEAR].
Any idea why ?

#####

EDIT 2 :
found out : loop2 starts, OUT done, IN skipped, jump, OUT skipped, IN done, exit
Not what i wanted to find, but anyway, it seems a delay is also needed between reading & writing...

#####

EDIT 3 :
Did some more tests.
It seems my initial theory was half-right.
I decided to create a dedicated topic about it.
« Last Edit: May 15, 2014, 02:23:31 am by the_mad_joob »

Offline the_mad_joob

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Re: WikiTI
« Reply #94 on: August 03, 2020, 01:09:05 pm »
https://wikiti.brandonw.net/index.php?title=83Plus:Ports:2F
Quote : "After every write to the LCD bit 1 of port 2 resets for a certain amount of time based on the current cpu speed and if the calculator is in hi speed mode."
It's actually working after every read aswell (tested with both ports $10 & $11).

https://wikiti.brandonw.net/index.php?title=83Plus:OS:Memory_Layout
The stack goes until $FFFE ($FFFF is actually unused by the system, that's right, an extra scrap byte).

https://wikiti.brandonw.net/index.php?title=Z80_Instruction_Set
Quote : "POP Same syntax as PUSH. Copies (SP) to regLSB, increments SP, copies (SP) to regMSB, then increments SP again. The word based at the starting value of SP is zeroed."
The last sentence is wrong and should be removed.
Also, ld J,N is missing, aswell as the following cycle wasters :
ld ixh,ixh
ld ixl,ixl
ld iyh,iyh
ld iyl,iyl

https://wikiti.brandonw.net/index.php?title=83Plus:OS:Certificate/Headers:Fields:Application_Headers
Quote : "In theory, it is legal to specify the master field as 800D xxxx if the application is less than 64 K in size. However, rabbitsign won't sign it."
It should be "800E" instead of "800D", or even more accurately "800DXX or 800EXXXX".

https://wikiti.brandonw.net/index.php?title=83Plus:OS:Raw_Flash_Commands
In the example code of the "Writing" section, using a "bit 5,(hl)" instruction is actually wrong.
Indeed, if the writing becomes successful after the xor (hl) instruction, reading (hl) again won't return status data anymore.
In other words, such algorithm could return a failure where there isn't any.
The right way to do it is to check both bits from a single reading.
Unoptimised replacement code :
Code: [Select]
...
programWaitLoop:
in a, (keyPort)
cp 0BFh
jr z, abortProgram
ld a, (hl)
ld c, a
xor b
bit 7, a
jr z, programDone
bit 5, c
jr z, programWaitLoop
abortProgram:
...

https://wikiti.brandonw.net/index.php?title=Category:83Plus:Ports:By_Address
Quote : "A note about 83+BE ports: On the 83+BE, many of the ports have been mirrored to the 00h-07h region. If a port is mirrored, when it is being read, take the bitwise-AND with 07h to find the actual port being accessed. All writes to mirrored ports are ignored."
https://wikiti.brandonw.net/index.php?title=83Plus:Ports:20
Quote : "The only side effect of this is that on the TI-83+ Basic this will cause both linkport lines to go high - which shouldn't matter too much if you're not using the linkport at that time, especially since both lines are high normally..."
Those 2 statements are contradictory.
If writings to mirrored ports are indeed ignored, how could writing to port $20 on the TI-83+BE be a probem ?

https://wikiti.brandonw.net/index.php?title=83Plus:OS:Variable_Storage_in_the_User_Archive
It's stated that a sector can start with $FC, anybody knows in which case ?
« Last Edit: September 12, 2020, 01:49:06 pm by the_mad_joob »

Offline Xeda112358

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Re: WikiTI
« Reply #95 on: August 03, 2020, 04:41:35 pm »
You can edit the pages on wikiti btw. As for the mirrored port writing being ignored, that's actually really handy to know. I suspect that two different people contributed those facts, or maybe it was he came person who forgot?