ZX Review #5-6 04 ноября 1997

Программирование     Ассемблер

Studies - Screen procedure "UP HL".

(C) In Vikulov, Tomsk


   I managed to reduce by 1
byte procedure UP, presented in ZX-Revue 4 / 95 by several 
authors (Paul Starikov, Edward K. and Andrew Vlasov). Here is a 
modification Text:

140.
UP DEC H

        LD A, H

        CPL

        AND 7

        RET NZ

        LD A, L

        SUB 32

        LD L, A

        RET C

        LD A, H

        ADD A, 8

        LD H, A

        RET
2

   I changed the design

        AND 7

        CP 7

        RET NZ


     at CPL

        AND 7

        RET NZ


   Generally, design

        AND N

        CP N

        JR NZ, LABEL
can be replaced by

        CPL

        AND N

        JR NZ, LABEL,
thus saving 1 byte, and increasing the speed by 3 cycles,
which is important when working with
graphics.


   Propose to introduce a "ZX-Review"
section "3D-graphics", which will
considered the problems and solutions related to the 
three-dimensional graphics on Spectrum'e. And I propose to 
introduce the section "Consultation", which will be addressed 
challenges and solutions associated with Spectrum'om. And now 
the first questions in this section. Why is the Pentagon-128 
begins to "shake" the screen? May be, it is connected with the 
signal INT? Why spontaneously printed symbols V, G, T, 5, B,

H, Y, 7? Perhaps this is due to overloading bus D7, so
as I have without buffering connected music coprocessor
or burned some resistors?


            *