Autobaud Detection - Analog Devices Blackfin ADSP-BF537 Hardware Reference Manual

Table 13-1. UART Bit Rate Examples With 100 MHz SCLK (Cont'd)
Bit Rate DL
38400 163
57600 109
115200 54
921600 7
6250000 1
Careful selection 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 ( ) of the general purpose timers. When working in
TACIx
mode these timers can be used to automatically detect the bit rate applied
to the pin by an external device. For more information, see
RX
"General-Purpose
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
ADSP-BF537 Blackfin Processor Hardware Reference
Actual % Error
38343.56 .147
57339.45 .452
115740.74 .469
892857.14 3.119
6250000 -
frequencies, that is, even multiples of
SCLK
Timers".
UCEN
UART Port Controllers
is not enabled while autobaud
WDTH_CAP
Chapter 15,
13-13