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BBC Micro Elite

Workspaces: ZP (Disc version)

Name: ZP [View in context] Type: Workspace Address: &0070 to &008B Category: Workspaces Summary: Important variables used by the loader
ORG &0070 .ZP SKIP 2 \ Stores addresses used for moving content around .P SKIP 1 \ Temporary storage, used in a number of places .Q SKIP 1 \ Temporary storage, used in a number of places .YY SKIP 1 \ Temporary storage, used in a number of places .T SKIP 1 \ Temporary storage, used in a number of places .SC SKIP 1 \ Screen address (low byte) \ \ Elite draws on-screen by poking bytes directly into \ screen memory, and SC(1 0) is typically set to the \ address of the character block containing the pixel \ we want to draw (see the deep dives on "Drawing \ monochrome pixels in mode 4" and "Drawing colour \ pixels in mode 5" for more details) .SCH SKIP 1 \ Screen address (high byte) .CHKSM SKIP 2 \ Used in the copy protection code ORG &008B .DL SKIP 1 \ Vertical sync flag \ \ DL gets set to 30 every time we reach vertical sync on \ the video system, which happens 50 times a second \ (50Hz). The WSCAN routine uses this to pause until the \ vertical sync, by setting DL to 0 and then monitoring \ its value until it changes to 30