PC312XDP512F0CFVR datasheet(505/1348 Pages) FREESCALE

Part #	PC312XDP512F0CFVR

Description	HCS12X Microcontrollers

PDF	1348 Pages

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Manufacturer	FREESCALE [Freescale Semiconductor, Inc]

Direct Link	http://www.freescale.com

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505 / 1348 page

Chapter 11 Serial Communication Interface (S12SCIV5)

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

505

In Figure 11-22 the veriﬁcation samples RT3 and RT5 determine that the ﬁrst low detected was noise and

not the beginning of a start bit. The RT clock is reset and the start bit search begins again. The noise ﬂag

is not set because the noise occurred before the start bit was found.

Figure 11-22. Start Bit Search Example 1

In Figure 11-23, veriﬁcation sample at RT3 is high. The RT3 sample sets the noise ﬂag. Although the

perceived bit time is misaligned, the data samples RT8, RT9, and RT10 are within the bit time and data

recovery is successful.

Figure 11-23. Start Bit Search Example 2

Reset RT Clock

Samples

RT Clock

RT Clock Count

Start Bit

RXD

LSB

Reset RT Clock

Samples

RT Clock

RT Clock Count

Actual Start Bit

RXD

LSB

Perceived Start Bit

PC312XDP512F0CFVR Datasheet(PDF) 505 Page - Freescale Semiconductor, Inc