UPSD3422_V01 datasheet(187/300 Pages) STMICROELECTRONICS

187 / 300 page

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UPSD3422, UPSD3433, UPSD3434, UPSD3454

Programmable counter array (PCA) with PWM

187/300

27.10

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.

27.11

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

= 0000h), and the smallest duty cycle is 0.0015% (CAPCOMHn CAPCOMLn = FFFFh). A

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

27.12

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 148 on page 187

through Table 150 on page 188). There is one PCA_STATUS register that covers both PCA0

and PCA1 (see Table 152 on page 188).

Table 148.

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

–

CLK_SEL[1:0]

Table 149.

PCA0 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.

EOVFI

1 = Enable Counter Overflow Interrupt if overflow flag (OVF) is set

4PCAIDLE

0 = PCA operates when CPU is in Idle Mode

1 = PCA stops running when CPU is in Idle Mode

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UPSD3422 Datasheet(PDF) 187 Page - STMicroelectronics

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