Introduction

The PWM module of TLSR8258 essentially compares the count value of the built-in counter with the set target count value. If they are the same, the level of the corresponding GPIO port will be reversed. If it is different, the state will remain unchanged.

The TLSR8258F512 supports 6-channel PWM(Pulse-Width-Modulation) output. Each PWM#n(n=0 ~ 5) has its corresponding inverted output at PWM#n_N pin. Refer to GPIO multiplexing function list to see which GPIOs support PWM functions.The clock source of the PWM module is the system clock.

Before describing the PWM mode, it is necessary to have some understanding of some design ideas of PWM. Among them, three very important concepts are waveform of signal frames, Invert PWM Output and Polarity for signal frame.

Waveform of Signal Frames

Assume that the level of the PWM is high in the count status. Set the number of cycles for the count status to cmp_cycle_num and set the number of cycles for a signal frame to max_cycle_num. As shown below, The workflow of the PWM module is as follows:

PWM module enter count status firstly, the level corresponding to the GPIO port will be pulled high
The current value of the built-in counter is compared with the set target value(cmp_cycle_num) to determine whether to reverse the level of the corresponding GPIO port. If they are equal, the GPIO level will be reversed, PWM module enter Remaining status.
The current value of the built-in counter is compared with the set target value(max_cycle_num) to determine whether to end the transmission of an old waveform frame and start the transmission of a new waveform frame

A Signal Frame of PWM

Invert PWM Output

By configuration we can directly invert the output of the PWM, which means that waveform of the corresponding PWM channel will be inverted completely.

A Inverted Signal Frame of PWM

Polarity for signal frame

The level of the PWM is high in the count status by default, which is configurable by the polarity(default: high). Configuring the polarity to be low and directly flipping the output level is the same effect. In other words, if the level of the PWM is set to low in the count status, waveform of the corresponding PWM channel will be also inverted completely.

A Inverted Signal Frame of PWM

PWM Mode

PWM module of TLSR8258 support five modes,including:

Continuous mode(normal mode,default): continuously send signal frame and NOT automatically stop
Counting mode: send a pulse group including many signal frams and stop
IR mode:continuously send many pulse groups and NOT automatically stop
IR FIFO mode: allow IR transmission of long code patterns without the continued intervention of MCU
IR DMA FIFO mode: this mode is similar to IR FIFO mode, except that the element is written into FIFO by DMA instead of MCU

NOTE:only PWM0 support all modes, while PWM1 ~ PWM5 only support Continuous mode.

Continuous Mode

PWM0 ~ PWM5 all support Continuous mode. In this mode, PWM module continuously sends out signal frames till it is stopped by configuration. when stopped, the PWM output will turn low immediately.

During Continuous mode, waveform could be changed freely via configuring cmp_cycle_num and max_cycle_num. New configuration will take effect in the next signal frame.

After each signal frame is finished, a frame interruption will be generated if the relevant interrupt configuration is turned on. for more detail ...

Block Diagram of Continuous Mode

Counting Mode

Only PWM0 supports Counting mode. In this mode, the number of signal frames PWM0 sends out can be defined.

After each signal frame is finished, a frame interruption will be generated. for more detail ...

Multiple signal frames can form a pulse group, after a pulse group is finished, PWM0 will be disabled auto maitically, and a pulse group interruption will be generated if the relevant interrupt configuration is turned on. for more detail ...

Block Diagram of Conuting Mode

IR Mode

Only PWM0 supports IR mode. In this mode, specified number of signal frames is defined as one pulse group. In contrast to Counting mode where PWM0 stops after first pulse group is finished, PWM0 will constantly send pulse groups in IR mode.

During IR mode, PWM0 output waveform could also be changed freely via configurating cmp_cycle_num , max_cycle_num and pulse_group_num. New configuration will take effect in the next pulse group.

To stop IR mode after completing current pulse group, user can switch PWM0 from IR mode to Counting mode so that PWM0 will completely send out current pulse group. If PWM0 is disabled, PWM0 output will turn Low immediately despite of current pulse group.

Block Diagram of IR Mode

IR FIFO Mode

Only PWM0 support IR FIFO mode. IR FIFO mode is designed to allow IR transmission of long code patterns without the continued intervention of MCU, and it is designed as a selectable working mode on PWM0. The IR carrier frequency is divided down from the system clock and can be configured as any normal IR frequencies, e.g. 36KHz,38KHz,40KHz,56KHz.

IR FIFO Mode define an element written into FIFO as basic unit of IR waveform. This element consists of 16bits, defined as follows: {#ELEM}

Bit[13:0]: set current number of pulse group(pulse_group_xx_num)
Bit[14]: select duty cycle (cmp_cycle_num) and period (max_cycle_num) for current pulse group
- 0: use configuration of cmp_cycle_num and max_cycle_num
- 1: use configuration of cmp_shadow_cycle_num and max_shadow_cycle_num
Bit[15]: determines whether current pulse group is used as carrier. in other words, this bit determine whether PWM will output pulse or low level
- 0: use low level as carrier, which means that PWM will output low level
- 1: use current pulse group as carrier, which means that PWM will output pulse waveform

The element is written into FIFO by 4-byte register. About FIFO, the description is as follows:

FIFO depth is 8 bytes
write an element including 16-bit to FIFO by API function
view FIFO status (empty or full) by API function
check FIFO data number by API function
long IR code process: if long IR code exceeds the FIFO depth, as long as FIFO is not overflow, user can continuously add waveforms to FIFO during IR waveforms sending
after all waveforms are sent, FIFO becomes empty. PWM0 will be disabled automatically
clear FIFO: only when the FIFO is NOT in active transmission, it can be cleared by API function

IR DMA FIFO Mode

Only PWM0 support IR DMA FIFO mode. This mode is similar to IR FIFO mode, except that the element is written into FIFO by DMA instead of MCU. User should configure the relative parameter for DMA, and then DMA will automatically write the configuration into FIFO. When DMA channel 5 is enabled, PWM will automatically output configured waveform, for more detail...

After all waveforms are sent, FIFO becomes empty. PWM0 will be disabled automatically.

PWM APIs List

In order to facilitate users to quickly develop products according to their own needs, TSI provide the following related APIs and examples.

APIs list	Description	Example	Update Date	Status
pwm_set_mode()	set the mode of PWM#n	API-PWM-CASE1	2019-1-10	Done
pwm_set_clk()	set the clock of PWM module	API-PWM-CASE1	2019-1-10	Done
pwm_set_cycle_and_duty()	set the max_cycle_num and cmp_cycle_num of PWM#n	API-PWM-CASE1	2019-1-10	Done
pwm_set_pwm0_shadow_cycle_and_duty()	set the shadow max_cycle_num and cmp_cycle_num of PWM	API-PWM-CASE3	2019-1-10	Done
pwm_set_pulse_num()	set pulse_group_num of PWM#n	API-PWM-CASE1	2019-1-10	Done
pwm_start()	start PWM#n	API-PWM-CASE1	2019-1-10	Done
pwm_stop()	stop PWM#n	-	2019-1-10	Done
pwm_revert()	revert output of PWM#n	-	2019-1-10	Done
pwm_n_revert()	revert output of PWM_n_#n	-	2019-1-10	Done
pwm_polo_enable()	set the polarity of PWM#n	-	2019-1-10	Done
pwm_config_dma_fifo_waveform()	set the carrier of PWM#n in IR DMA FIFO Mode	API-PWM-CASE5	2019-1-10	Done
pwm_set_dma_address()	set the address for DMA	API-PWM-CASE5	2019-1-10	Done
pwm_start_dma_ir_sending()	start PWM0 in IR DMA FIFO mode to send data	API-PWM-CASE5	2019-1-10	Done
pwm_stop_dma_ir_sending()	stop PWM0 in IR DMA FIFO mode to send data	API-PWM-CASE5	2019-1-10	Done

TSI provides the following examples of this module to help users quickly understand and apply related modules.

Examples list	Description	Update Date	Status
API-PWM-CASE1	PWM in Continuous Mode	2019-1-10	Done
API-PWM-CASE2	PWM in Counting Mode	2019-1-10	Done
API-PWM-CASE3	PWM in IR Mode	2019-1-10	Done
API-PWM-CASE4	PWM in IR FIFO Mode	2019-1-10	Done
API-PWM-CASE5	PWM in IR DMA FIFO Mode	2019-1-10	Done

History Record

Date	Description	Author
2019-1-10	initial release	LJW
2019-8-15	update api name for application	LJW