# The Firmware Guide - CRTC Registers

To change the value of these registers, the register number should be output on address &BCxx and then the data output on &BDxx

Reg | Function | Default Value |  |  |  |  | Reg | Function | Default Value
R0 | Horizontal Total | 63 |  |  |  |  | R1 | Horizontal Displayed | 40
R2 | Horizontal Sync Pos. | 46 |  |  |  |  | R3 | Sync Width | 112
R4 | Vertical Total | 38 |  |  |  |  | R5 | Vertical Total Adjust | 0
R6 | Vertical Displayed | 25 |  |  |  |  | R7 | Vertical Sync Position | 30
R8 | Interlace and Skew | 0 |  |  |  |  | R9 | Maximum Raster Addr | 7
R10 | Cursor Start Raster | 0 |  |  |  |  | R11 | Cursor End Raster | 0
R12 | Start Address (H) | 48 |  |  |  |  | R13 | Start Address (L) | 0
R14 | Cursor Register (H) | 192 |  |  |  |  | R15 | Cursor Register (L) | 07

#### David Cantrell, May 1996