NAME
pcppi —
PC (ISA) control and timer port
driver
SYNOPSIS
pcppi* at isa?
spkr0 at pcppi?
DESCRIPTION
The pcppi driver handles resource
allocation and device attachment for the ports related to the ISA speaker in
the traditional PC/AT “design”. These are the “system
control port” (which was implemented by the 8255 “PPI”
in the XT, hence the name of this driver) at I/O address 0x61 and the first
8253 timer at 0x40-0x43.
The pcppi driver provides its child
devices with the ability to output simple tones through the PC speaker. The
speaker(4) device uses this to synthesize sounds. It also provides
helper functions to the
pckbd(4) driver as a substitute for a “keyboard beep”,
because the PC keyboard hardware doesn't provide this.