UPSD3312D datasheet(159/272 Pages) STMICROELECTRONICS

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UPSD33xx

Programmable counter array (PCA) with PWM

Doc ID 9685 Rev 7

159/272

26.10

PWM mode - fixed frequency, 10-bit

The 10-bit PWM logic requires that all 3 TCMs in PCA0 or PCA1 operate in the same 10-bit

PWM mode. The 10-bit PWM operates in a similar manner as the 16-bit PWM, except the

PCACHm and PCACLm counters are reconfigured as 10-bit counters. The CAPCOMHn and

CAPCOMLn registers become 10-bit registers.

PWM duty cycle of each TCM module can be specified in the 10-bit CAPCOMHn and

CAPCOMLn registers. When the 10-bit PCA counter is equal or greater than the values in

the 10-bit registers CAPCOMHn and CAPCOMLn, the PWM output switches to a high state.

When the 10-bit PCA counter overflows, the PWM pin is switched to a logic low and starts

the next PWM pulse.

The most-significant 6 bits in the PCACHm counter and CAPCOMH register are “Don’t

cares” and have no effect on the PWM generation.

26.11

Writing to capture/compare registers

When writing a 16-bit value to the PCA Capture/Compare registers, the low byte should

always be written first. Writing to CAPCOMLn clears the E_COMP Bit to '0'; writing to

CAPCOMHn sets E_COMP to '1' the largest duty cycle is 100% (CAPCOMHn CAPCOMLn

= 0x0000), and the smallest duty cycle is 0.0015% (CAPCOMHn CAPCOMLn = 0xFFFF). A

0% duty cycle may be generated by clearing the E_COMP Bit to ‘0’.

26.12

Control register bit definition

Each PCA has its own PCA_CONFIGn, and each module within the PCA block has its own

TCM_Mode register which defines the operation of that module (see Table 103 on page 159

through Table 105 on page 160). There is one PCA_STATUS register that covers both PCA0

and PCA1 (see Table 107 on page 161).

Table 103.

PCA0 Control register PCACON0 (SFR 0A4h, Reset Value 00h)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

EN-ALL

EN_PCA

EOVFI

PCAIDLE

–

10B_PWM

CLK_SEL[1:0]

Table 104.

PCACON0 register bit definition

Bit

Symbol

Function

7EN-ALL

0 = No impact on TCM modules

1 = Enable both PCA counters simultaneously

(override the EN_PCA Bits)

This bit is to start the two 16-bit counters in the

PCA. For customers who want 5 PWM, for

example, this bit can start all of the PWM outputs.

6EN_PCA

0 = PCA counter is disabled

1 = PCA counter is enabled

EN_PCA Counter Run Control Bit. Set with

software to turn the PCA counter on. Must be

cleared with software to turn the PCA counter off.

UPSD3312D Datasheet(PDF) 159 Page - STMicroelectronics

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