SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 147

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

On-Chip Peripheral Components
7.9
Oscillator and Clock Circuit
XTAL1 and XTAL2 are the input and output of a single-stage on-chip inverter which can be
configured with off-chip components as a Pierce oscillator. The oscillator, in any case, drives the
internal clock generator. The clock generator provides the internal clock signals to the chip at half
the oscillator frequency. These signals define the internal phases, states and machine cycles, as
described in chapter 3.
Figure 7-65 shows the recommended oscillator circuit.
Figure 7-65
Recommended Oscillator Circuit
In this application the on-chip oscillator is used as a crystal-controlled, positive-reactance oscillator
(a more detailed schematic is given in figure 7-66). lt is operated in its fundamental response mode
as an inductive reactor in parallel resonance with a capacitor external to the chip. The crystal
specifications and capacitances are non-critical. In this circuit 30 pF can be used as single
capacitance at any frequency together with a good quality crystal. A ceramic resonator can be used
C
C
in place of the crystal in cost-critical applications. lt a ceramic resonator is used,
and
are
1
2
normally selected to be of somewhat higher values, typically 47 pF. We recommend consulting the
manufacturer of the ceramic resonator for value specifications of these capacitors.
Semiconductor Group
148