
Semiconductor Group 5 - 17
On-Chip Peripheral Components
5.4.2 Serial Channel 1 Baud Rate Generator
A new baud rate generator for Serial Channel 1 now offers a wider range of selectable baud rates.
Especially a baud rate of 1200 baud can be achieved now.
The baud rate generator itself is identical with the one used for Serial Channel 0. It consists of a free
running 10-bit timer with F
OSC
/2 input frequency. On overflow of this timer there is an automatic
reload from the registers S1RELL (address 9D
H
) and S1RELH (address BB
H
). The lower 8 bits of
the timer are reloaded from S1RELL, while the upper two bits are reloaded from bit 0 and 1 of
register S1RELH. The baud rate timer is reloaded by writing to S1RELL.
The baud rate in mode A and B can be determined by the following formula:
with S1REL = S1RELH.1 – 0, S1RELL.7 – 0
Figure 5-6 shows a block diagram of the baud rate generator for Serial Interface 1.
Figure 5-6
Baud Rate Generator for Serial Interface 1
Mode A, B baud rate =
oscillator frequency
32 x (2
10
– S1REL)
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