XC886/888CLM
Serial Interfaces
User’s Manual
12-39
V1.3, 2010-02
Serial Interfaces, V 1.0
12.3.1.6
Baud Rate Generation
The serial channel SSC has its own dedicated 16-bit baud-rate generator with 16-bit
reload capability, allowing baud rate generation independent of the timers.
shows the baud-rate generator.
Figure 12-16 SSC Baud-rate Generator
The baud-rate generator is clocked with the module clock
f
PCLK
. The timer counts
downwards. Register BR is the dual-function Baud-rate Generator/Reload register.
Reading BR, while the SSC is enabled, returns the contents of the timer. Reading BR,
while the SSC is disabled, returns the programmed reload value. In this mode, the
desired reload value can be written to BR.
Note: Never write to BR while the SSC is enabled.
The formulas below calculate either the resulting baud rate for a given reload value, or
the required reload value for a given baud rate:
<BR> represents the contents of the reload register, taken as an unsigned 16-bit integer,
while baud rate is equal to
f
MS_CLK/SS_CLK
.
The maximum baud rate that can be achieved when using a module clock of 24 MHz is
12 MBaud in master mode (with <BR> = 0000
H
) or 6 MBaud in slave mode (with
<BR> = 0001
H
).
lists some possible baud rates together with the required reload values and
the resulting deviation errors, assuming a module clock frequency of 24 MHz.
2
.
.
16-Bit Counter
16-Bit Reload Register
f
PCLK
f
MS_CLK/SS_CLK
f
MS_CLK max
in Master Mode
<
f
PCLK
/2
f
SS_CLK max
in Slave Mode
<
f
PCLK
/4
- 1
BR =
Baud rate =
2
x (<BR> + 1)
f
PCLK
f
PCLK
2
x
Baud rate
*
Содержание XC886CLM
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