] >On the MSX interrupts the interrupt ends with a EI:RET. (No RETI, it has no
] >use).
]
] But it has a reason I forgot. What's the actual effect of RETI? What are
] the differences with an EI/RET? And with an EI/RETI?
It is mainly a feature for hardwaredevelopers that use the Z80 as a
microcon
At 09:17 PM 7/22/99 +0200, you wrote:
>Example: You have an interrupt which during the interruptroutine. At the end
>this results in one extra word on the stack, and the interrupt will be
>restarted. But if the interrupt once again occurs during the
>interruptroutine you'll get 2 words on the sta
> >The reason why EI enabled the interrupt 1 instruction later had indeed to
do
> >with the interrupt. If you let the interrupt end with EI:RET then the
> >interrupts will be enabled AFTER the RET, hence preventing a stack
overload
> >when the interrupt-routines occasionally takes too long and can
> >On the MSX interrupts the interrupt ends with a EI:RET. (No RETI, it has
no
> >use).
>
> But it has a reason I forgot. What's the actual effect of RETI? What are
> the differences with an EI/RET? And with an EI/RETI?
Well according to the documentation the purpose of RETI is so
interrupt-gener
> >Keep in mind that when executing an EI the interrupts will be enabled
after
> >the next instruction. So this is the way to keep the interrupts disabled
as
> >short as possible, which is always preferred (although not required).
>
> I just wondered... Does DI have this behaviour as well? If so,
On Thu, 22 Jul 1999, MkII wrote:
> But it has a reason I forgot. What's the actual effect of RETI?
RETI is the same thing as RET, only with a different opcode.
Some Z80-based devices can detect the opcode of RETI when it's on
the data bus, and by doing this they can know when i
At 04:59 PM 7/21/99 +0200, you wrote:
>The reason why EI enabled the interrupt 1 instruction later had indeed to do
>with the interrupt. If you let the interrupt end with EI:RET then the
>interrupts will be enabled AFTER the RET, hence preventing a stack overload
>when the interrupt-routines occa
>On the MSX interrupts the interrupt ends with a EI:RET. (No RETI, it has no
>use).
But it has a reason I forgot. What's the actual effect of RETI? What are
the differences with an EI/RET? And with an EI/RETI?
MARK 2
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At 09:11 PM 7/20/99 +0200, you wrote:
>Like this:
>LD A,value
>DI
>OUT (#99),a
>LD A,register+128
>EI
>OUT (#99),a
>
>Keep in mind that when executing an EI the interrupts will be enabled after
>the next instruction. So this is the way to keep the interrupts disabled as
>short as possible, which
> >Keep in mind that when executing an EI the interrupts will be enabled
after
> >the next instruction. So this is the way to keep the interrupts disabled
as
> >short as possible, which is always preferred (although not required).
>
> Nice tip. This reminds me of the EI/RETI pair back in the ZX er
>> Should I disable interrupts accessing the VDP register directly?
>
>Yes.
>
>Like this:
>LD A,value
>DI
>OUT (#99),a
>LD A,register+128
>EI
>OUT (#99),a
>
>Keep in mind that when executing an EI the interrupts will be enabled after
>the next instruction. So this is the way to keep the interrupts
At 03:56 AM 7/20/99 +0200, you wrote:
>Is it possible to execute BDOS / Disk BASIC disk operation with interrupts
>disabled?
Yes.
>Do those functions embed EIs?
Yes.
>Should I disable interrupts accessing the VDP register directly?
You don't have to, but it does solve the F700 slowdown.
Or
> Is it possible to execute BDOS / Disk BASIC disk operation with interrupts
> disabled?
Errm... It surely is possible I'm not sure if they keep the interrupts
disabled. Actually, I think they re-enable them afterwards.
> Do those functions embed EIs?
??? I guess so.
> Should I disable inter
Is it possible to execute BDOS / Disk BASIC disk operation with interrupts
disabled?
Do those functions embed EIs?
Should I disable interrupts accessing the VDP register directly?
Is it legal to call 256 times #FD9F with interrupts disabled at VDP level?
Is it legal to tell Disk ROM to stop th
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