Texas Instruments CDT370, User Manual

Page: 53 / 83

Running Title—Attribute Reference
6-1 Chapter Title—Attribute Reference
Clock Source
You can select an alternate clock setting through the Configuration dialog box
in the Load menu. Please refer to
Setting Up The Clock in the TMS370 Family
C Source Debugger User’s Guide. The crystal option is not available on the
CDT370.
The choices are:
-
OSCILLATOR: If you select OSCILLATOR from the menu, the debugger
will reset the TMS370 device with Osc 2 as the clock. If there is not a
usable clock signal at Osc 2, the device will use Osc 1. The CDT370 20
MHz oscillator (location Osc 1) is used to generate the default clock. You
can also plug in another oscillator at Osc 2, to work at any allowed fre-
quency. Osc 2 is the highest priority device.
-
TARGET: If you select TARGET, the CPU expects the clock input from the
target system. A clock buffer circuitry is found in the target cable head, so
the external clock can be a crystal.
As a result, the target clock source can be:
1) A crystal connected between low and high input lead on the target connec-
tor (the crystal driver of the target connector will generate the clock for the
CDT370 board).
2) An oscillator driving low input lead on the target connector.
If you change the clock source, the debugger tries to reset the TMS370 device
with the new clock source. If the emulator detects that the device is not operat-
ing properly, it rejects the new clock source and resets the chip again, restoring
the old clock.
When this occurs, an error message is displayed:
source not available for clock
source is the clock source you tried to select.
Chapter 6