C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 112

• Manufacturer Part Number: C505_9708
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

6.3.3.3.2 Using Timer 1 to Generate Baud Rates
In mode 1 and 3 of the serial port also timer 1 can be used for generating baud rates. Then the baud
rate is determined by the timer 1 overflow rate and the value of SMOD as follows:
The timer 1 interrupt is usually disabled in this application. Timer 1 itself can be configured for either
"timer" or "counter" operation, and in any of its operating modes. In most typical applications, it is
configured for "timer" operation in the auto-reload mode (high nibble of TMOD = 0010 B ). In this
case the baud rate is given by the formula:
Very low baud rates can be achieved with timer 1 if leaving the timer 1 interrupt enabled,
configuring the timer to run as 16-bit timer (high nibble of TMOD = 0001 B ), and using the timer 1
interrupt for a 16-bit software reload.
Semiconductor Group
Mode 1, 3 baud rate =
Mode 1, 3 baud rate =
2
2
SMOD
32
SMOD
6-50
32 x 6 x (256 – (TH1))
x oscillator frequency
x
(timer 1 overflow rate)
On-Chip Peripheral Components
C505 / C505C
1997-08-01