ACT apricot - Tone Generation

SOUND GENERATION
Tone Generation
To generate a audio tone, initially requires the tone
generator to be
programmed with three bytes of
information,
and the three other generators to be switched
off. The first two bytes determine the frequency of the audio
tone and the third byte determines the level of the produced
audio tone.
Once programmed with the frequency data, the tone
generator
can be switched on and off, using the level control
byte alone.
The frequency of the audio tone is set by a IO-bit word
which forms part of the first two bytes. The remaining bits
of the frequency bytes select the tone generator register and
differentiate between the byte containing selection bits and
the byte containing frequency data only. The format of the
frequency bytes and the expression used to calculate the
tone frequency is as follows.
F = 10
6
/ 16n where F is the tone frequency and
n
is the la-bit binary number in
decimal format.
D7 DO
11 I R21 Rl I RO I F3
1
F21
Fl I Fl I FIRST FREQUENCY BYTE
I " I
~---LSB Frequency bits
"""'------- Register selection
a...,...... _______ Byte differentiation
D7
DO
I 0 I x I F91 F81 F71 F61 F51 F41 SECOND FREQUENCY BYTE
I
'
I
.... 1----- MSB Frequency bits
..... -------- Logic state immaterial
J....-- ________ Byte differentiation