35 lines
1.1 KiB
Text
35 lines
1.1 KiB
Text
|
// This file is part of www.nand2tetris.org
|
||
|
|
// and the book "The Elements of Computing Systems"
|
||
|
|
// by Nisan and Schocken, MIT Press.
|
||
|
|
// File name: tools/builtIn/Screen.hdl
|
||
|
|
|
||
|
|
/**
|
||
|
|
* The Screen (memory map).
|
||
|
|
* Functions exactly like a 16-bit 8K RAM:
|
||
|
|
* 1. out(t)=Screen[address(t)](t)
|
||
|
|
* 2. If load(t-1) then Screen[address(t-1)](t)=in(t-1)
|
||
|
|
*
|
||
|
|
* The built-in chip implementation has the side effect of continuously
|
||
|
|
* refreshing a visual 256 by 512 black-and-white screen, simulated
|
||
|
|
* by the simulator. Each row in the visual screen is represented
|
||
|
|
* by 32 consecutive 16-bit words, starting at the top left corner
|
||
|
|
* of the visual screen. Thus the pixel at row r from the top and
|
||
|
|
* column c from the left (0<=r<=255, 0<=c<=511) reflects the c%16
|
||
|
|
* bit (counting from LSB to MSB) of the word found in
|
||
|
|
* Screen[r*32+c/16].
|
||
|
|
*/
|
||
|
|
|
||
|
|
CHIP Screen {
|
||
|
|
|
||
|
|
IN in[16], // what to write
|
||
|
|
load, // write-enable bit
|
||
|
|
address[13]; // where to read/write
|
||
|
|
OUT out[16]; // Screen value at the given address
|
||
|
|
|
||
|
|
BUILTIN Screen;
|
||
|
|
CLOCKED in, load;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|