Maxim-integrated MAXQ622 Bedienungsanleitung PDF herunterladen (Seite 145)

MAXQ612/MAXQ622 User’s Guide

Maxim Integrated 9-9

The below formulas can be used to calculate the output of the baud-clock generator and the resultant mode 1, 3 baud

rates. Additionally, a table has been provided giving example phase register (PR) settings needed to produce some

more common baud rates at certain system clock frequencies (assuming SMOD = 1).

Baud-Clock Generator Output (BAUD) = System Clock Frequency x PR/2

Baud Rate for Modes 1 and 3 = BAUD x 2

(SMODx2)

9.3 Framing Error Detection

A framing error occurs when a valid stop bit is not detected. This results in the possible improper reception of the serial

word. The USART can detect a framing error and notify the software. Typical causes of framing errors are noise and

contention. The framing error condition is reported in the SCON register for the USART.

The framing error bit, FE, is located in SCON.7. Note that this bit normally serves as SM0 and is described as SM0/FE_0

in the register description. Framing error information is made accessible by the FEDE (framing error-detection enable)

bit located at SMD.0. When FEDE is set to 1, the framing error information is shown in SM0/FE (SCON.7). When FEDE

is set to 0, the SM0 function is accessible. The information for bits SM0 and FE is actually stored in different registers.

Changing FEDE only modifies which register is accessed, not the contents of either.

Table 9-3. Example Baud-Clock Generator Settings (SMOD = 1)

Figure 9-5. Baud-Clock Generator

15 0

ADDITION

BAUD-CLOCK OUTPUT =

CARRY OUT FROM PHASE ACCUMULATOR [16]

PHASE ACCUMULATOR

SYSTEM CLOCK

FREQUENCY (MHz)

BAUD RATE

(PR SETTING)

SYSTEM CLOCK

FREQUENCy (MHz)

BAUD RATE

(PR SETTING)

115200 (5E5F)

57600 (2F30)

19200 (0FBB)

9600 (07DD)

2400 (01FF)

3.579545

57600 (83D2)

19200 (2BF1)

9600 (15F8)

2400 (057E)

115200 (75F7)

57600 (3AFB)

19200 (13A9)

9600 (09D5)

2400 (0275)

2.4576

57600 (C000)

19200 (4000)

9600 (2000)

2400 (0800)

3.6864

115200 (FFFF)

57600 (8000)

19200 (2AAB)

9600 (1555)

2400 (0555)

19200 (9D49)

9600 (4EA5)

2400 (13A9)

1 2 ... 140 141 142 143 144 145 146 147 148 149 150 ... 254 255

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