ADSP-BF537 Blackfin Processor Hardware Reference
13-13
UART Port Controllers
L
Careful selection of
SCLK
frequencies, that is, even multiples of
desired bit rates, can result in lower error percentages.
Note that the UART module is clocked 16 times faster than the bit clock.
This is required to oversample bits on reception and to generate RZI code
in IrDA mode.
Autobaud Detection
At the chip level, the UART RX pins are routed to the alternate capture
inputs (
TACIx
) of the general purpose timers. When working in
WDTH_CAP
mode these timers can be used to automatically detect the bit rate applied
to the
RX
pin by an external device. For more information, see
The capture capabilities of the timers are often used to supervise the bit
rate at runtime. If the Blackfin UART was talking to any device supplied
by a weak clock oscillator that drifts over time, the Blackfin can re-adjust
its UART bit rate dynamically as required.
Often, autobaud detection is used for initial bit rate negotiations. There,
the Blackfin processor is most likely a slave device waiting for the host to
send a predefined autobaud character as discussed below. This is exactly
the scenario used for UART booting. In this scenario, it is recommended
that the UART clock enable bit
UCEN
is not enabled while autobaud
38400
163
38343.56
.147
57600
109
57339.45
.452
115200
54
115740.74
.469
921600
7
892857.14
3.119
6250000
1
6250000
-
Table 13-1. UART Bit Rate Examples With 100 MHz SCLK (Cont’d)
Bit Rate
DL
Actual
% Error
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...