ADSP-BF50x Blackfin Processor Hardware Reference
15-21
UART Port Controllers
operation—all derived from
SCLK
—the pulse widths can be used to calcu-
late the bit rate divider for the UART by using the following formula:
In order to increase the number of timer counts and therefore the resolu-
tion of the captured signal, it is recommended not to measure just the
pulse width of a single bit, but to enlarge the pulse of interest over more
bits. Traditionally, a NULL character (ASCII 0x00) was used in autobaud
detection, as shown in
Figure 15-6
.
Because the example frame in
Figure 15-6
encloses 8 data bits and 1 start
bit, apply the following formula:
Real UARTxRX signals often have asymmetrical falling and rising edges,
and the sampling logic level is not exactly in the middle of the signal volt-
age range. At higher bit rates, such pulse width-based autobaud detection
might not return adequate results without additional analog signal condi-
tioning. Measuring signal periods works around this issue and is strongly
recommended.
For example, predefine ASCII character “@” (0x40) as the autobaud
detection character and measure the period between two subsequent fall-
ing edges. As shown in
Figure 15-7
, measure the period between the
Figure 15-6. Autobaud Detection Character 0x00
DIVISOR
TIMERx _WIDTH
16
1
EDB0
–
Number of captured UART bits
-----------------------------------------------------------------------------------------------------------------
·
=
FRAME WIDTH
S
1
2
3
4
5
6
7
STOP
0
DIVISOR
TIMERx _WIDTH
16
1
EDB0
–
9
---------------------------------------------
=
Содержание EZ-KIT Lite ADSP-BF506F
Страница 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 132: ...Unique Information for the ADSP BF50x Processor 4 22 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 342: ...Unique Information for the ADSP BF50x Processor 7 106 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 484: ...Unique Information for the ADSP BF50x Processor 10 60 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 493: ...ADSP BF50x Blackfin Processor Hardware Reference 11 9 Core Timer Unique Information for the ADSP BF50x Processor None ...
Страница 494: ...Unique Information for the ADSP BF50x Processor 11 10 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 506: ...Unique Information for the ADSP BF50x Processor 12 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 544: ...Unique Information for the ADSP BF50x Processor 13 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 712: ...Unique Information for the ADSP BF50x Processor 16 62 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 972: ...Unique Information for the ADSP BF50x Processor 20 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...