C165_96 Datasheet, PDF (236/283 Pages) Siemens Semiconductor Group – 16-Bit CMOS Single-Chip Microcontrollers

10Jul97@15:33h
System Reset / C165/C163
The following describes the different selections that are offered for reset configuration. The default
modes refer to pins at high level, ie. without external pulldown devices connected. Please also
consider the note (above) on reserved pins.
Emulation Mode
Pin P0L.0 (EMU) selects the Emulation Mode, when low during reset. This mode allows the access
to integrated XBUS peripherals via the external bus interface pins in application specific versions of
the C165/C163. In addition also the RSTOUT pin floats to tristate rather than be driven low. When
the emulation mode has been latched the CLKOUT output is automatically enabled.
This mode is used for special emulator purposes and is of no use in basic C165/C163 devices, so
in this case P0L.0 should be held high.
Default: Emulation Mode is off.
Note: In emulation mode the direct drive clock option is selected with P0.15 (P0H.7) = ’1’.
Adapt Mode
Pin P0L.1 (ADP) selects the Adapt Mode, when low during reset. In this mode the C165/C163 goes
into a passive state, which is similar to its state during reset. The pins of the C165/C163 float to
tristate or are deactivated via internal pullup/pulldown devices, as described for the reset state. In
addition also the RSTOUT pin floats to tristate rather than be driven low, and the on-chip oscillator
is switched off.
This mode allows switching a C165/C163 that is mounted to a board virtually off, so an emulator
may control the board’s circuitry, even though the original C165/C163 remains in its place. The
original C165/C163 also may resume to control the board after a reset sequence with P0L.1 high.
Default: Adapt Mode is off.
Note: When XTAL1 is fed by an external clock generator (while XTAL2 is left open), this clock
signal may also be used to drive the emulator device.
However, if a crystal is used, the emulator device’s oscillator can use this crystal only, if at
least XTAL2 of the original device is disconnected from the circuitry (the output XTAL2 will
still be active in Adapt Mode).
Bootstrap Loader Mode
Pin P0L.4 (BSL) activates the on-chip bootstrap loader, when low during reset. The bootstrap loader
allows moving the start code into the internal RAM of the C165 via the serial interface ASC0. The
C165 will remain in bootstrap loader mode until a hardware reset with P0L.4 high or a software
reset.
Default: The C165 starts fetching code from location 00’0000_H, the bootstrap loader is off.
Note: The bootstrap loader is not available in the C163.
Semiconductor Group
15-8