Maxim Integrated MAXQ610 - Manual (Page 134)

9-9
MAXQ610 User’s Guide
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 17
Baud Rate for Modes 1 and 3 = BAUD x 2 (SMODx2) /2 6
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
0
15 0
PR
16
ADDITION
BAUD-CLOCK OUTPUT =
CARRY OUT FROM PHASE ACCUMULATOR [16]
0
PHASE ACCUMULATOR
SYSTEM CLOCK
FREQUENCY (MHz)
BAUD RATE
(PR SETTING)
SYSTEM CLOCK
FREQUENCy (MHz)
BAUD RATE
(PR SETTING)
10
115200 (5E5F)
57600 (2F30)
19200 (0FBB)
9600 (07DD)
2400 (01FF)
3 .579545
57600 (83D2)
19200 (2BF1)
9600 (15F8)
2400 (057E)
8
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)
1
19200 (9D49)
9600 (4EA5)
2400 (13A9)