SAB80C515A-5 Datasheet, PDF (43/108 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller Family

On-Chip Peripheral Components
Figure 5-5 shows a block diagram of the options available for baud rate generation of Serial
Channel. It is a fully compatible superset of the functionality of the SAB 80C515. The new baud rate
generator can be used in modes 1 and 3 of the Serial Channel. It is activated by setting bit BD
(ADCON.7). This also starts the baud rate timer. When Timer1 shall be used for baud rate
generation, bit BD must be cleared. In any case, bit SMOD (PCON.7) selects an additional divider
by two.
The default values after reset in registers SRELL and SRELH provide a baud rate of 4.8 kBaud (with
SMOD = 0) or 9.6 kBaud (with SMOD = 1) at 12 MHz oscillator frequency. This guarantees full
compatibility to the SAB 80C515.
Figure 5-5
Block Diagram of Baud Rate Generation for Serial Interface
If the new baud rate generator is used the baud rate of the Serial Channel in Mode 1 and 3 can be
determined as follows:
2^SMOD x oscillator frequency
Mode 1, 3 baud rate =
; with SREL = SRELH.1 – 0, SRELL.7 – 0
64 x (2¹⁰ – SREL)
SREL = 2¹⁰ –
f 2^SMOD x _OSC
64 x baud rate
Semiconductor Group
5-10