Si3220/25 Si3200/02
Rev. 1.3
65
Not
Recommended
fo
r N
ew
D
esi
gn
s
To enable automatic cadence for tone generator 1,
define the OSC1TA and OSC1TI registers and set the
OSC1TAEN and OSC1TIEN bits. This enables each of
the timers to control the state of the oscillator enable bit,
OSC1EN. The 16-bit counter counts until the active
timer expires, at which time the 16-bit counter resets to
zero and begins counting until the inactive timer
expires. The cadence continues until the user clears the
OSC1TA and OSC1TIEN control bits. Setting the
ZEROEN1 bit implements the zero crossing detect
feature. This ensures that each oscillator pulse ends
without a dc component. The timing diagram in
Figure 36 is an example of an output cadence that uses
the zero crossing feature.
One-shot oscillation is possible with OSC1EN and
OSC1TAEN.
Direct
control
over
the
cadence
is
achieved by setting the OSC1EN
bit directly
if
OSC1TAEN and OSC1TIEN are disabled.
The operation of tone generator 2 is identical to that of
tone generator 1 using its respective control registers.
Note: Tone Generator 2 should not be enabled simultane-
ously with the ringing oscillator because of resource
sharing within the hardware.
Table 35. Register and RAM Locations Used for Tone Generation
Tone Generator 1
Parameter
Register/RAM
Mnemonics
Register/RAM Bits
Description/Range
(LSB Size)
Oscillator 1 Frequency
Coefficient
OSC1FREQ
OSC1FREQ[15:3]
Sets oscillator frequency
Oscillator 1 Amplitude Coeffi-
cient
OSC1AMP
OSC1AMP[15:0]
Sets oscillator amplitude
Oscillator 1 Initial Phase
Coefficient
OSC1PHAS
OSC1PHAS[15:0]
Sets initial phase
(default = 0)
Oscillator 1 Active Timer
O1TALO/O1TAHI
OSC1TA[15:0]
0 to 8.19 s (125 s)
Oscillator 1 Inactive Timer
O1TILO/O1TIHI
OSC1TI[15:0]
0 to 8.19 s (125 s)
Oscillator 1 Control
OMODE, OCON
FSKSSEN, OSC1FSK,
ZEROEN1, ROUT1,
ENSYNC1, OSC1TAEN,
OSC1TIEN, OSC1EN
Enables all Oscillator 1
parameters
Oscillator 1 Interrupts
IRQVEC1, IRQEN1
OS1TAS, OS1TIS, OS1-
TAE, OS1TIE
Interrupt enable/status
Tone Generator 2
Parameter
Location
Register/RAM Address
Description/Range
Oscillator 2 Frequency
Coefficient
OSC2FREQ
OSC2FREQ[15:3]
Sets oscillator frequency
Oscillator 2 Amplitude Coeffi-
cient
OSC2AMP
OSC2AMP[15:0]
Sets oscillator amplitude
Oscillator 2 Initial Phase
Coefficient
OSC2PHAS
OSC2PHAS[15:0]
Sets initial phase
(default = 0)
Oscillator 2 Active Timer
O2TALO/O2TAHI
OSC2TA[15:0]
0 to 8.19 s (125 s)
Oscillator 2 Inactive Timer
O2TILO/O2TIHI
OSC2TI[15:0]
0 to 8.19 s (125 s)
Oscillator 2 Control
OMODE, OCON
ZEROEN2, ROUT2,
ENSYNC2, OSC2TAEN,
OSC2TIEN, OSC2EN
Enables all Oscillator 2
parameters
Oscillator 2 Interrupts
IRQVEC1, IRQEN1
OS2TAS, OS2TIS, OS2-
TAE, OS2TIE
Interrupt enable/status