C505-2RM SIEMENS [Siemens Semiconductor Group], C505-2RM Datasheet - Page 35

• Manufacturer Part Number: C505-2RM
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Serial Interface (USART)
The serial port is full duplex and can operate in four modes (one synchronous mode, three
asynchronous modes) as illustrated in table 8.
Table 8
USART Operating Modes
Mode
0
1
2
3
For clarification some terms regarding the difference between "baud rate clock" and "baud rate"
should be mentioned. In the asynchronous modes the serial interfaces require a clock rate which is
16 times the baud rate for internal synchronization. Therefore, the baud rate generators/timers have
to provide a "baud rate clock" (output signal in figure 14 to the serial interface which - there divided
by 16 - results in the actual "baud rate". Further, the abbrevation f
frequency (crystal or external clock operation).
The variable baud rates for modes 1 and 3 of the serial interface can be derived either from timer 1
or from a decdicated baud rate generator (see figure 14).
Semiconductor Group
SM0
0
0
1
1
SCON
SM1
0
1
0
1
Description
Shift register mode, fixed baud rate
Serial data enters and exits through R D; T D outputs the shift
clock; 8-bit are transmitted/received (LSB first)
8-bit UART, variable baud rate
10 bits are transmitted (through T D) or received (at R D)
9-bit UART, fixed baud rate
11 bits are transmitted (through T D) or received (at R D)
9-bit UART, variable baud rate
Like mode 2
35
OSC
refers to the oscillator
C505A / C505CA
C505 / C505C
1997-12-01