OS_Map, PipeDream map control

Owned by Gunther Strube
Last updated: May 16, 2012Version comment
4 min read

Register parameters

RST 20H, DEFW $F406
IN:
     BC = reason code
          MP_WR ($01)    write a line to the map
          MP_DEF ($02)   define a map using the Panel default width
          MP_GRA ($03)   define a map of specific width
          MP_DEL ($04)   no functionality
          MP_MEM ($05)   define a map of specific width and associate to application segment

OUT, if call successful:
     Fc = 0
OUT, if call failed:
     Fc = 1
     A = error code:
          RC_BAD ($04), bad parameters (errors are generally ignored)
          RC_UNK ($03), value of BC is not valid

Registers changed after return:
     defined by MP_ reason code.

 

MP_WR

MP_WR ($01), write a line to the map
IN:
     A = window ID number (ASCII digit '1' to '6')
     DE = row of the map to be written (0 to 63, 0 = top of screen)
     HL = points to bytes to be written
OUT:
     -

Registers changed after return:
     ..BCDEHL/IXIY same
     AF....../.... different

Notes

HL points to a series of bytes, where each byte represents 8 pixels on the map. Bit 7 is the left most pixel and the bytes are written onto the map from left to right. The number of bytes read from HL depends on the width of the map.


MP_DEF

MP_DEF ($02), define a map using the Panel width
IN:
     A = window ID number (ASCII digit '1' to '6')
OUT:
     B = width of map in pixels
     C = width of map in 6 bit characters

Registers changed after return:
     A...DEHL/IXIY same
     .FBC..../.... different

Notes

This call simply reads the value of the map size entry in the Panel and attempts to define a map of that width.


MP_GRA

MP_GRA ($03), define a map of specific width
IN:
     A = window ID number (ASCII digit '1' to '6')
     HL = width of map to set up (0 to 255)
OUT:
     as for MP_DEF

MP_DEL

MP_DEL ($04), delete a map
IN:
     A = window ID number (ASCII digit '1' to '6')
OUT:
     -

Notes

This call executes no functionality.


MP_MEM

MP_MEM ($05), define a map of specific width and associate to application segment (OZ V4.2 and newer)
IN:
     A = window ID number (ASCII digit '1' to '6')
     B = MS_Sx segment for returned map memory as extended address
     HL = width of map to set up (0 to 255), modulus 8
OUT:
     D = width of map in pixels
     E = width of map in 6 bit characters
     C = MS_Sx segment for returned map memory as extended address
     BHL = extended address of base of map area (for MS_Sx segment), upper left (0,0) coordinate
          (size of map area is D * 64 pixels = size/8 bytes)

Registers changed after return:
     A......./IXIY same
     .FBCDEHL/.... different

Notes

A map has always 64 pixels height (depth of screen). When the map is created, just use OS_Mpb (or RST OZ_MPB in OZ 4.1 and newer)  to bind returned BHL pointer into C = MS_Sx segment. An example:

        ld      a,'4'             ; use window '4' for graphics
        ld      B, MS_S2
        ld      C, MP_MEM
        ld      hl,64
        oz      OS_Map            ; create a map of 64 pixels
        rst     OZ_Mpb            ; and bind map memory to segment 2
        ld      (hl),@10101010    ; write first 8 pixels to the map area, which is automatically displayed on screen

MP_MEM only exists in OZ V4.2 and newer. If used on older ROMs, Fc = 1 is returned (invalid reason code).


At present there is only one map area and it is reclaimed for text by redefining the window in which it sits, or by defining a window which overlaps it. However, to allow for future expansion this call should be used if a map area is to be reclaimed for text use. Please refer to section The Map Area, to know more about. How the map pixel memory is organised.



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