LPC2917 datasheet(38/68 Pages) PHILIPS

38 / 68 page

LPC2917_19_1

Preliminary data sheet

Rev. 1.01 — 15 November 2007

38 of 68

NXP Semiconductors

LPC2917/19

ARM9 microcontroller with CAN and LIN

• Automotive dimmer controller: The flexibility of providing waves of a desired duty

cycle and cycle period allows the PWM to control the amount of power to be

transferred to the load. The PWM functions as a dimmer controller in this application

• Motor controller: The PWM provides multi-phase outputs, and these outputs can be

controlled to have a certain pattern sequence. In this way the force/torque of the

motor can be adjusted as desired. This makes the PWM function as a motor drive.

The PWM block diagram in Figure 10 shows the basic architecture of each PWM. PWM

functionality is split into two major parts, a VPB domain and a PWM domain, both of which

run on clocks derived from the BASE_MSCSS_CLK. This split into two domains affects

behavior from a system-level perspective. The actual PWM and prescale counters are

located in the PWM domain but system control takes place in the VPB domain.

The actual PWM consists of two counters; a 16-bit prescale counter and a 16-bit PWM

counter. The position of the rising and falling edges of the PWM outputs can be

programmed individually. The prescale counter allows high system bus frequencies to be

scaled down to lower PWM periods. Registers are available to capture the PWM counter

values on external events.

Note that in the Modulation and Sampling SubSystem, each PWM has its individual clock

source CLK_MSCSS_PWMx (x runs from 0 to 3). Both the prescale and the timer

counters within each PWM run on this clock CLK_MSCSS_PWMx, and all time references

are related to the period of this clock. See Section 8.8 for information on generation of

these clocks.

8.7.6.3

Synchronizing the PWM counters

A mechanism is included to synchronize the PWM period to other PWMs by providing a

sync input and a sync output with programmable delay. Several PWMs can be

synchronized using the trans_enable_in/trans_enable_out and sync_in/sync_out ports.

See Section 8.7.2.1 for details of the connections of the PWM modules within the MSCSS

in the LPC2917/19. PWM 0 can be master over PWM 1; PWM 1 can be master over

PWM 2, etc.

Fig 10. PWM block diagram

PWM

control

registers

PWM

Counter,

prescale

counter

shadow

registers

VPB system bus

update

Capture data

Config data

IRQ’s

Sync_in

Capture inputs

IRQ capt_match

PWM domain

VPB domain

IRQ pwm

Match outputs

PWM counter value

Transfer_enable_in

Transfer_enable_out

Sync_out

Carier inputs

Trap input

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