Commodore Plus 4 - Page 318

306 Machine Language on the Commodore Plus/4
Operating System Subroutine Descriptions
$FF81 CINT
Registers Altered: .A, .X9 .Y
Initializes the screen editor. This subroutine performs such functions as setting
up default I/O devices (keyboard and screen), the text window, and the current
character
color. It clears the screen to all blanks with character color black.
$FF84 IOINIT
Registers Altered: .A, .X
Initializes the I/O devices. This subroutine performs such functions as setting
up the graphics chip and the DMA disk.
SFF87 RAMTAS
Registers Altered: .A9 .X, .Y
Performs a RAM test. This subroutine performs such functions as clearing
zero page and pages 2, 3, 4, and 7, setting the top and bottom of memory, and
defining the function keys. Call it before any of these areas are initialized, or
otherwise they will be overwritten.
$FF8A RESTOR
Registers Altered: .A, .X, .Y
Restores the vectors to their initial values. This subroutine sets up the vectors
at $0312-$0331 from ROM, performing such functions as directing IRQ and
BRK service to the appropriate addresses.
$FF8D VECTOR
Registers Altered: .A, .Y
When called with the carry clear, loads the vectors at $0312-$0331 from a
designated section of memory. Before calling this subroutine, set .X to the low
address to load the vectors from, and .Y to the high address to load the vectors
from. Be certain none of the vectors will be used during the loading process (e.g.,
disable interrupts). When called with the carry set, this subroutine reads the
vectors and stores their values in the designated section of memory. Before calling
it, set .X to the low address to store the vectors to, and . Y to the high address to
store the vectors to.