c8051f410 Silicon Laboratories, c8051f410 Datasheet - Page 208

• Manufacturer Part Number: c8051f410
• Description: 2.0 V, 32/16 Kb Flash, Smartclock, 12-bit Adc
• Manufacturer: Silicon Laboratories

C8051F410/1/2/3
22.1. Enhanced Baud Rate Generation
The UART0 baud rate is generated by Timer 1 in 8-bit auto-reload mode. The TX clock is generated by
TL1; the RX clock is generated by a copy of TL1 (shown as RX Timer in Figure 22.2), which is not user-
accessible. Both TX and RX Timer overflows are divided by two to generate the TX and RX baud rates.
The RX Timer runs when Timer 1 is enabled, and uses the same reload value (TH1). However, an
RX Timer reload is forced when a START condition is detected on the RX pin. This allows a receive to
begin any time a START is detected, independent of the TX Timer state.
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see
Counter/Timer with Auto-Reload” on page 233
flows will occur at two times the desired UART baud rate frequency. Note that Timer 1 may be clocked by
one of six sources: SYSCLK, SYSCLK / 4, SYSCLK / 12, SYSCLK / 48, the external oscillator clock / 8, or
an external input T1. The UART0 baud rate is determined by Equation 22.1-A and Equation 22.1-B.
Where T1
auto-reload mode reload value). Timer 1 clock frequency is selected as described in
on page 231
through Table 22.6. Note that the internal oscillator may still generate the system clock when the external
oscillator is driving Timer 1.
208
CLK
. A quick reference for typical baud rates and system clock frequencies is given in Table 22.1
is the frequency of the clock supplied to Timer 1, and T1H is the high byte of Timer 1 (8-bit
Detected
Start
B)
A)
Figure 22.2. UART0 Baud Rate Logic
UartBaudRate
T1_Overflow_Rate
RX Timer
Equation 22.1. UART0 Baud Rate
Timer 1
TH1
TL1
=
Overflow
Overflow
Rev. 1.0
). The Timer 1 reload value should be set so that over-
1
-- -
2
×
=
T1_Overflow_Rate
------------------------- -
256 TH1
T1
–
CLK
2
2
UART
Section “24.1.3. Mode 2: 8-bit
RX Clock
TX Clock
Section “24. Timers”