Operating Modes
Triple Timer Module
9
-19
9.3.3
Pulse Width Modulation (PWM, Mode 7)
In Mode 7, the timer generates periodic pulses of a preset width. When the counter equals the
value in the TCPR, the
TIO
output signal is toggled and TCSR[TCF] is set. The contents of the
counter are placed into the TCR. If the TCSR[TCIE] bit is set, a compare interrupt is
generated. The counter continues to increment on each timer clock.
If counter overflow occurs, the
TIO
output signal is toggled, TCSR[TOF] is set, and an
overflow interrupt is generated if the TCSR[TOIE] bit is set. If the TCSR[TRM] bit is set, the
counter is loaded with the TLR value on the next timer clock and the count resumes. If the
TCSR[TRM] bit is cleared, the counter continues to increment on each timer clock. This
process repeats until the timer is disabled.
When the TCSR[TE] bit is set and the counter starts, the
TIO
signal assumes the value of INV.
On each subsequent toggle of the
TIO
signal, the polarity of the
TIO
signal is reversed. For
example, if the INV bit is set, the
TIO
signal generates the following signal: 1010. If the INV
bit is cleared, the
TIO
signal generates the following signal: 0101.
The value of the TLR determines the output period ($FFFFFF
−
TLR + 1). The timer counter
increments the initial TLR value and toggles the
TIO
signal when the counter value exceeds
$FFFFFF. The duty cycle of the
TIO
signal is determined by the value in the TCPR. When the
value in the TLR increments to a value equal to the value in the TCPR, the
TIO
signal is
toggled. The duty cycle is equal to ($FFFFFF – TCPR) divided by ($FFFFFF
−
TLR + 1). For
a 50 percent duty cycle, the value of TCPR is equal to ($ TLR + 1)/2.
Note:
The value in TCPR must be greater than the value in TLR.
Bit Settings
Mode Characteristics
TC3
TC2
TC1
TC0
Mode
Name
Function
TIO
Clock
0
1
1
1
7
Pulse width modulation
PWM
Output
Internal
Summary of Contents for DSP56303
Page 1: ...DSP56303 User s Manual 24 Bit Digital Signal Processor DSP56303UM AD Revision 1 January 2001 ...
Page 52: ...JTAG OnCE Interface 2 22 DSP56303 User s Manual ...
Page 114: ...General Purpose Input Output GPIO 5 10 DSP56303 User s Manual ...
Page 212: ...GPIO Signals and Registers 8 26 DSP56303 User s Manual ...
Page 268: ...Interrupt Equates A 22 DSP56303 User s Manual ...
Page 306: ...Programming Sheets B 38 DSP56303 User s Manual ...
Page 320: ...Index 14 DSP56303 User s Manual ...