SAB80C517 Datasheet, PDF (41/61 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller

SAB 80C517/80C537
Serial Interface 0
Serial Interface 0 can operate in 4 modes:
Mode 0:
Shift register mode:
Serial data enters and exits through RXD0. TXD0 outputs the shift clock 8 data bits
are transmitted/received (LSB first). The baud rate is fixed at 1/12 of the oscillator
frequency.
Mode 1:
8-bit UART, variable baud rate:
10-bit are transmitted (through RXD0) or received (through RXD0): a start bit (0),
8 data bits (LSB first), and a stop bit (1). On reception, the stop bit goes into RB80
in special function register S0CON. The baud rate is variable.
Mode 2:
9-bit UART, fixed baud rate:
11-bit are transmitted (through TXD0) or received (through RXD0): a start bit (0),
8 data bits (LSB first), a programmable 9th, and a stop bit (1). On transmission, the
9th data bit (TB80 in S0CON) can be assigned to the value of 0 or 1. For example,
the parity bit (P in the PSW) could be moved into TB80 or a second stop bit by
setting TB80 to 1. On reception the 9th data bit goes into RB80 in special function
register S0CON, while the stop bit is ignored. The baud rate is programmable to
either 1/32 or 1/64 of the oscillator frequency.
Mode 3:
9-bit UART, variable baud rate:
11-bit are transmitted (through TXD0) or received (through RXD0): a start bit (0),
8 data bits (LSB first), a programmable 9th, and a stop bit (1). In fact, mode 3 is the
same as mode 2 in all respects except the baud rate. The baud rate in mode 3 is
variable.
Variable Baud Rates for Serial Interface 0
Variable baud rates for modes 1 and 3 of serial interface 0 can be derived from either timer 1
or from the oscillator via a special prescaler ("BD").
Timer 1 may be operated in mode 1 (to generate slow baud rates) or mode 2. The dedicated
baud rate generator "BD" provides the two standard baud rates 4800 or 9600 baud with 0.16%
deviation. Table 8 shows possible configurations and the according baud rates.
SAB 80C517 devices with stepping code "CA" or later provide a dedicated baud rate generator
for the serial interface 0. This baud rate genertaor is a free running 10-bit timer with
programmable reload registers.
Mode 1.3 baud rate = -6---4-----_×--2--_-^S---2-^M---1-^O--0--^D---_–-^×---S-^f--^O--0--^S-R--^C---E----L----_-
The default value after reset in the reload registers S0RELL and S0RELH prvide a baud rate
of 4.8 kBaud (SMOD = 0) or 9.6 kBaud (SMOD = 1) at 12 MHz oscillator frequency. This
guarantees full compatibility to the SAB 80C517 older steppings.
Semiconductor Group
40