C167CS datasheet(187/517 Pages) INFINEON

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C167CS

Derivatives

Dedicated Pins

User’s Manual

8-3

V2.0, 2000-07

The Oscillator Input XTAL1 and Output XTAL2 connect the internal Main Oscillator

to the external crystal. The oscillator provides an inverter and a feedback element. The

standard external oscillator circuitry (see Chapter 6) comprises the crystal, two low end

capacitors and series resistor to limit the current through the crystal. The main oscillator

is intended for the generation of the basic operating clock signal of the C167CS.

An external clock signal may be fed to the input XTAL1, leaving XTAL2 open or

terminating it for higher input frequencies.

The Reset Input RSTIN allows to put the C167CS into the well defined reset condition

either at power-up or external events like a hardware failure or manual reset. The input

voltage threshold of the RSTIN pin is raised compared to the standard pins in order to

minimize the noise sensitivity of the reset input.

In bidirectional reset mode the C167CS’s line RSTIN may be driven active by the chip

logic e.g. in order to support external equipment which is required for startup (e.g. flash

memory).

Bidirectional reset reflects internal reset sources (software, watchdog) also to the RSTIN

pin and converts short hardware reset pulses to a minimum duration of the internal reset

sequence. Bidirectional reset is enabled by setting bit BDRSTEN in register SYSCON

and changes RSTIN from a pure input to an open drain IO line. When an internal reset

is triggered by the SRST instruction or by a watchdog timer overflow or a low level is

applied to the RSTIN line, an internal driver pulls it low for the duration of the internal

reset sequence. After that it is released and is then controlled by the external circuitry

alone.

The bidirectional reset function is useful in applications where external devices require

a defined reset signal but cannot be connected to the C167CS’s RSTOUT signal, e.g.

an external flash memory which must come out of reset and deliver code well before

RSTOUT can be deactivated via EINIT.

The following behavior differences must be observed when using the bidirectional reset

feature in an application:

• Bit BDRSTEN in register SYSCON cannot be changed after EINIT and is cleared

automatically after a reset.

• The reset indication flags always indicate a long hardware reset.

• The PORT0 configuration is treated like on a hardware reset. Especially the bootstrap

loader may be activated when P0L.4 is low.

• Pin RSTIN may only be connected to external reset devices with an open drain output driver.

• A short hardware reset is extended to the duration of the internal reset sequence.

C167CS Datasheet(PDF) 187 Page - Infineon Technologies AG