ST72324B datasheet(164/167 Pages) STMICROELECTRONICS

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ST72324B

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PUSH CC

SIM

reset interrupt flag

POP CC

15.1.5 16-bit Timer PWM Mode

In PWM mode, the first PWM pulse is missed after

writing the value FFFCh in the OC1R register

(OC1HR, OC1LR). It leads to either full or no PWM

during a period, depending on the OLVL1 and

OLVL2 settings.

15.1.6 SCI Wrong Break duration

Description

A single break character is sent by setting and re-

setting the SBK bit in the SCICR2 register. In

some cases, the break character may have a long-

er duration than expected:

- 20 bits instead of 10 bits if M=0

- 22 bits instead of 11 bits if M=1.

In the same way, as long as the SBK bit is set,

break characters are sent to the TDO pin. This

may lead to generate one break more than expect-

ed.

Occurrence

The occurrence of the problem is random and pro-

portional to the baudrate. With a transmit frequen-

19200

baud

(fCPU=8MHz

and

SCI-

BRR=0xC9), the wrong break duration occurrence

is around 1%.

Workaround

If this wrong duration is not compliant with the

communication protocol in the application, soft-

ware can request that an Idle line be generated

before the break character. In this case, the break

duration is always correct assuming the applica-

tion is not doing anything between the idle and the

break. This can be ensured by temporarily disa-

bling interrupts.

The exact sequence is:

- Disable interrupts

- Reset and Set TE (IDLE request)

- Set and Reset SBK (Break Request)

- Re-enable interrupts

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