NRF9E5 Datasheet, PDF (84/104 Pages) List of Unclassifed Manufacturers – 433/868/915MHz RF Transceiver with Embedded 8051 Compatible Microcontroller and 4 Input, 10 Bit ADC

PRODUCT SPECIFICATION
nRF9 E5 Single Chip Transceiver with Embedded Microcontroller and ADC
18.9.2 Mode 1
Mode 1 provides standard asynchronous, full-duplex communication, using a total of ten
bits: one start bit, eight data bits, and one stop bit. For receive operations, the stop bit is
stored in RB8. Data bits are received and transmitted LSB first.
18.9.2.1 Mode 1 Baud Rate
The mode 1 baud rate is a function of timer overflow. Serial port can use either Timer 1
or Timer 2 to generate baud rates. Each time the timer increments from its maximum
count (0xFF for Timer 1 or 0xFFFF for Timer 2), a clock is sent to the baud-rate circuit.
The clock is then divided by 16 to generate the baud rate. When using Timer 1, the
SMOD bit selects whether or not to divide the Timer 1 rollover rate by 2. Therefore,
when using Timer 1, the baud rate is determinedby the equation:
2^SMOD
Baud Rate =
x Timer 1 Overflow
32
SMOD is SFR bit PCON.7
When using Timer 2, the baud rate is determined by the equation:
Baud Rate = ^{Timer 2 Overflow}
16
To use Timer 1 as the baud-rate generator, it is best to use Timer 1 mode 2 (8-bit counter
with auto-reload), although any counter mode can be used. The Timer 1 reload value is
stored in the TH1 register, which makes the complete formula for Timer 1:
Baud Rate = ^2SMOD x
clk
32 4 x (256 - TH1)
The 4 in the denominator in the above equation can be obtained by setting the T1M bit
in the CKCON SFR. To derive the required TH1 value from a known baud rate (when
TM1 = 0), use the equation:
TH1 = 256 - ^{2 SMOD ∗ clk}
128 ∗ Baud Rate
You can also achieve very low serial port baud rates from Timer 1 by enabling the
Timer 1 interrupt, configuring Timer 1 to mode 1, and using the Timer 1 interrupt to
initiate a 16-bit software reload. Table Table 72 lists sample reload values for a variety
of common serial port baud rates.
Main office: Nordic Semiconductor ASA - Vestre Rosten 81, N-7075 Tiller, Norway -Phone [phone] - Fax [phone]
Revision: 1.1
Page 84 of 104
June 2004