LM3S9BN5 Datasheet, PDF (1114/1380 Pages) Texas Instruments – Stellaris® LM3S9BN5 Microcontroller

Pulse Width Modulator (PWM)
21.3.7
21.3.8
■ Module-Level Register: PWMENABLE (based on the state of the ENUPDn bits in the PWMENUPD
register).
■ Generator Register: PWMnGENA, PWMnGENB, PWMnDBCTL, PWMnDBRISE, and
PWMnDBFALL (based on the state of various Update mode bits and fields in the PWMnCTL
register (GENAUPD; GENBUPD; DBCTLUPD; DBRISEUPD; DBFALLUPD)).
All other registers are considered statically provisioned for the execution of an application or are
used dynamically for purposes unrelated to maintaining synchronization and therefore do not need
synchronous update functionality.
Fault Conditions
A fault condition is one in which the controller must be signaled to stop normal PWM function and
then set the PWMn signals to a safe state. Two basic situations cause fault conditions:
■ The microcontroller is stalled and cannot perform the necessary computation in the time required
for motion control
■ An external error or event is detected
The PWM generator can use the following inputs to generate a fault condition, including:
■ FAULTn pin assertion
■ A stall of the controller generated by the debugger
■ The trigger of an ADC digital comparator
Fault conditions are calculated on a per-PWM generator basis. Each PWM generator configures
the necessary conditions to indicate a fault condition exists. This method allows the development
of applications with dependent and independent control.
Four fault input pins (FAULT0-FAULT3) are available. These inputs may be used with circuits that
generate an active High or active Low signal to indicate an error condition. A FAULTn pins may be
individually programmed for the appropriate logic sense using the PWMnFLTSEN register.
The PWM generator's mode control, including fault condition handling, is provided in the PWMnCTL
register. This register determines whether the input or a combination of FAULTn input signals and/or
digital comparator triggers (as configured by the PWMnFLTSRC0 and PWMnFLTSRC1 registers)
is used to generate a fault condition. The PWMnCTL register also selects whether the fault condition
is maintained as long as the external condition lasts or if it is latched until the fault condition until
cleared by software. Finally, this register also enables a counter that may be used to extend the
period of a fault condition for external events to assure that the duration is a minimum length. The
minimum fault period count is specified in the PWMnMINFLTPER register.
Status regarding the specific fault cause is provided in the PWMnFLTSTAT0 and PWMnFLTSTAT1
registers.
PWM generator fault conditions may be promoted to a controller interrupt using the PWMINTEN
register.
Output Control Block
The output control block takes care of the final conditioning of the pwmA' and pwmB' signals before
they go to the pins as the PWMn signals. Via a single register, the PWM Output Enable
(PWNENABLE) register, the set of PWM signals that are actually enabled to the pins can be modified.
1114
Texas Instruments-Production Data
January 21, 2012