zx spectrum 128k mb-02+ dma hc200 didaktik scorpion atm pentagon putting themnmnmnmnemonic in mnmnmncoding SCREEN MODES- INTRODUCTION -There are four screen modes used in the Coupe, each using varying amounts of memory and each having different attributes for use by the programmer.The hardware pointers which display the contents of the memory are controlled by the VMPR, Video Memory Page Register (252 dec). By using the lower 5 bits of this register we can access up to 32pages of video screen memory. It must be noted that modes 3 and 4use 24 kilo-bytes, which go over the page boundary of 16kilobybtes. Where this happens, the video addressing hardware wraps into the next page within the same block. For example: By entering page 12 to the VMPR, video wraps to page 13The same applies to any page and the principal of even to odd always applies. - MODE 1 -32 cells x 24 lines in 2 colours from 16 out of a palette of 128colours, giving 768 character cells (8 x 8) using 6 kilobytes of bit mapped memory and 0.75 kilo-bytes of attribute memory. This mode emulates Spectrum memory mapping. - MODE 2 -32 cells x 192 lines in 2 colours from 16 out of a palette of 128colours, giving 6144 character cells (8 x 1) using 6 kilobytes of bit mapped memory and 6 kilobytes of attribute memory. This mode has contiguous memory addressing in two blocks. - MODE 3 -512 pixels x 192 lines in 4 colours out of a palette of 128 colours,giving 98304 dots using 24 kilo-bytes of memory. This mode, when used ...
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