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using Manic Miner and Jet Set Willy game engines
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Message: 6633
Author: andrewbroad
Date: 17/02/2010
Subject: Re: Patch-vectors in JSW64
Roger wrote:
>Room 63 uses the main-loop patch-vector (Room-offsets #FD-FE) to call a subroutine at #C500.
> I downloaded your JSW 64V version 0.01 HL 12.tap file from WoS
> expecting that it would make the perfect template file for future
> 64V games but I ran into trouble with Room 63 straight away because
> any guardians placed there behave like the eye sprite in the clock
> tower even when this has been deleted. They attempt to jump around
> a non-existent clock face.
>
> I presume that this special guardian path must have been done with a
> patch that remains in that room. Can it be removed with a poke so
> that the room can be re-used like any other?
The address of Room r's main-loop patch-vector is
bank : #C0FD + #200*(r mod 32)
where
bank = 1 if {0 <= r <= 31}
bank = 3 if {32 <= r <= 63}
bank = 4 if {64 <= r <= 95}
bank = 6 if {96 <= r <= 127}
Thus, the address of Room 63's main-loop patch-vector is
3:#C0FD + #200*31 = 3:#FEFD
The default patch-vector is #869F, which just returns.
To make Room 63 use the default patch-vector, set:
3:#FEFD: 9F 86
> Are there instructions published anywhere on how to call aTo do that, you need to write a room-setup patch-vector (Room-offsets #FB-FC) to apply the poke, and a default patch-vector that is called by every other room in the game to set the normal conditions.
> subroutine in free memory that would poke something on room entry
> and then how would normal conditions be regained on leaving the
> room?
An example of this is documented in my Advanced MM/JSW Trainer, which makes guardians harmless by default, but certain rooms call a room-setup patch-vector to make them harmful:
http://abroad.sqweebs.com/spectrum/software/trainer.html
(download v0.1.0 and see TECHNICA.TXT: sections "Default room-setup patch-vector" and "Harmful guardians").
--
Dr. Andrew Broad
http://abroad.sqweebs.com/spectrum/mmjsw/
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