Specifications

3-1
C
HAPTER
3
E
NHANCED
S
OUND
O
UTPUT
Introduction
The Series 3 and Series 3a provide distinct sets of sound services.
The Series 3 as supplied can emit only buzzer sounds, DTMF dialling tones, and simple alarm sounds.
However, by loading a suitable device driver, such as SNDFRC.LDD, the machine can also be made to
emit sequences of musical notes of variable duration, thus greatly extending its sound capabilities. The
first section of this chapter describes use of the SNDFRC.LDD attached device driver from within a simple
demonstration program.
The Series 3a has considerably greater sound capabilities than the Series 3. In addition to emitting buzzer
sounds, DTMF dialling tones and simple alarm sounds, the Series 3a can play simultaneously two
sequences of musical notes, and can play and record digital sound files - for details of playing and
recording digital sound files see the General System Services chapter of the Plib Reference manual. The
second section of this chapter describes a simple program that demonstrates the playing of sequences of
notes using the built-in
SND:
device driver.
Warning: any attempt to load and use the SNDFRC.LDD attached device driver on the Series 3a is a
serious error - the machine will in all probability hang, necessitating a soft reset.
Sound on the Series 3
Introduction
This section explains how to create a wider range of musical sound output, via the loudspeaker, than is
possible by merely using the Series 3's built-in
SND:
device driver.
These services rely on a dynamic extension to the Series 3 operating system, known as a loadable device
driver.
With this device driver installed, strings of sound covering two octaves in semitone intervals can be
generated. Control is also possible over the duration and loudness of the notes emitted.
The sndfrc and snddvr device drivers
The chapter Example Device Drivers in the Additional System Information manual describes two different
enhanced sound drivers, sndfrc.ldd and snddvr.ldd, from the point of view of how to write device drivers.
The current chapter focuses on the question, not how to write these drivers, but how to use them.
In fact, this chapter only considers the driver sndfrc.ldd, which is arguably the superior of the two. See
Example Device Drivers for a discussion on how the two device drivers differ.
Once this device driver file has been installed, a device with the name
MUS:
can be opened by applications.
Installing sndfrc.ldd
Any program which wishes to use the services of sndfrc.ldd needs to check, during its initialisation, that
this driver has been installed. This is necessary because, in contrast to some other device drivers such as
the serial port device driver and the basic sound device driver, the
MUS:
device driver is not built into the
ROM of the Series 3.