I'm about to finish my lunch break, sorry if I sound slightly short...
1) is there any pattern or logic to the values placed on the bus
during interrupts? I guess an equivalent question is: what realistic
options do I have on the Sam for catching and processing interrupts?
2) are there any
On Tue, May 20, 2008 at 02:03:57PM +0100, Thomas Harte wrote:
I'm about to finish my lunch break, sorry if I sound slightly short...
1) is there any pattern or logic to the values placed on the bus
during interrupts? I guess an equivalent question is: what realistic
options do I have on the
On Tue, May 20, 2008 at 03:22:54PM +0100, Andrew Collier wrote:
correction:
ld a,h 4
sla l 8
rla4
add table/256 8
ld h,a 4
= 28
You can also shave a little more time if you're willing to rearrange the table:
Instead of word pairs (low
While thinking about it during the afternoon, I have decided that
since this table is absolutely fundamental to my program (it's part of
the table based 2.8x2.8 multiply), I'm just going to centre it on
address 0. Then I can cut the ld bc and the add hl, bc. I'm happy to
rearrange my
On Tue, May 20, 2008 at 07:20:48PM +0100, Thomas Harte wrote:
Obviously the second is faster — but I'm curious about your cycle
counts. All the z80 documentation I have lists add hl, ss as 11 t-
states. Why have you turned that into 16?
By mistake :)
I'm working from google, and misread
1)
Normally the value is FF and it looks pretty stable too considering PRO-DOS
uses IM 2 without a vector table. So your choices are IM 0/IM 1 both do a
RST 38H or IM 2 which 'calls' the adress found at the address pointed by I
register (MSB) and the value on the databus (LSB). Like the
Mode 2 uses a table with 128 word address but as byte high,byte low not the
normal low, high bytes
So if you set your org/dump address to ??FF (i.e. ??00-1)
and then do
DEFWmode2.i,mode2.i
so you have 129 words.
mode2.i:
di
push
Surely set would only work if I had an unsigned offset from the
beginning of a table? I'm using a signed offset from the middle of a
table.
On 20 May 2008, at 19:48, Edwin Blink wrote:
1)
Normally the value is FF and it looks pretty stable too considering
PRO-DOS uses IM 2 without a
From: Thomas Harte
Surely set would only work if I had an unsigned offset from the beginning
of a table? I'm using a signed offset from the middle of a table.
it works the same as ADD HL,HL ADD HL,BC the difference is
you store the table entries LSB,MSB so you need the ADD HL,HL
First you
Boy Do I feel silly I missed that ADD HL,BC.
Edwin
- Original Message -
From: Thomas Harte [EMAIL PROTECTED]
To: sam-users@nvg.ntnu.no
Sent: Tuesday, May 20, 2008 9:53 PM
Subject: Re: Short, short questions
Surely set would only work if I had an unsigned offset from the
Hi,
I'm sceptical about this claim. I've never heard anybody say that the
vector formed is big-endian - it's just you don't know the byte offset
from which the interrupt vector will be fetched. (As Edwin says, it is
usually 255 - which is odd so your 1-aligned table will usually work -
This was based on info from a book called z-80 Workshop manual by E.A Parr.
The I register gives the high part of the table and the hardware gives the
low part to the table then takes that word for the service routine. So if
you start from one byte before the table and use the same address for
I've just been looking at my books. Although I can't find the bit that said
about swapping to high,low but I'm sure that I did read it somewhere. It
does say that the device only gives the bits 1-7 and bit 0 is always 0
giving 128 possible addresses.
Dave
- Original Message -
From:
Hi,
In a spirit of scientific enquiry, let us perform an experiment by
running the code below.
On SimCoupe, at least, the border turns bright yellow, meaning it ran
the interrupt vector at 0x9a92 (that is, the 256th and 257th bytes of
the table). Anybody got real hardware handy?
All 8 bits are used for LSB of the vector. The part where bit 0 always is
zero is when one of the Z80's IO chips is connected (PIO,SIO,CTC etc) is
connected.
Edwin
- Original Message -
From: David Brant [EMAIL PROTECTED]
To: sam-users@nvg.ntnu.no
Sent: Wednesday, May 21, 2008 1:02
I thought the idea of mode2 was you could have different vectors for
different devices connected well this throws a spanner in the works. But
then again is there any hardware for the SAM that uses them? I think it must
have been an old spectrum book that said this about swapping high,low bytes.
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