SAB80C515A-5 Datasheet, PDF (91/108 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller Family

SAB 80C515A/83C515A-5
The Serial Interface can operate in 4 modes:
Mode 0: Shift register mode:
Serial data enters and exits through R × D. T × D outputs the shift clock 8 data bits
are transmitted/received (LSB first). The baud rate is fixed at 1/12 of the oscillator fre-
quency.
Mode 1: 8-bit UART, variable baud rate:
10-bit are transmitted (through T × D) or received (through R × D): 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 SCON. The baud rate is variable.
Mode 2: 9-bit UART, fixed baud rate:
11-bit are transmitted (through T × D) or received (through R × D): 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 SCON) can be assigned to the value of 0 or 1. For example, the par-
ity 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 SCON,
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 T × D) or received (through R × D): 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 vari-
able.
Variable Baud Rates for Serial Interface
Variable baud rates for modes 1 and 3 of serial interface can be derived from either timer 1 or
a new dedicated Baudrate Generator.
The baud rate is generated by a free running 10-bit timer with programmable reload register.
Mode 1.3 baud rate = ^{2 SMOD * fOSC}
64 * (2¹⁰ - SREL)
The default value after reset in the reload registers SRELL and SRELH provides a baud rate of
4.8 kBaud (SMOD = 0) or 9.6 kBaud (SMOD = 1) at 12 MHz oscillator frequency. This guaran-
tees full compatibility to the SAB 80C515.
Semiconductor Group
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