Description
The "unrecognized device" error message is issued when the Jam File (.jam) is not receiving the device ID it expects. One reason that it may
not get the appropriate information is that the data may be inverted.
The source code for the Jam Player is implemented with a parallel port configuration which requires an inversion of the
TDO input. Therefore,
the software, by default, inverts the TDO input to retrieve the actual
value.
jam_jtag_io(), in the jamstub.c file, is the routine where data is read from the port. The following line of code shows where the routine
reads the value on TDO:
tdo = (read_byteblaster(1) & 0x80) ? 0 : 1;
This line of code inverts the value on TDO (the TDO value is passed from read_byteblaster()). The following line of code is what a non-inverted value would look like:
tdo = (read_byteblaster(1) & 0x80) ? 1 : 0;
When the embedded processor does not invert the TDO input, then the
code should be configured as shown in the second example above.
| For more detailed information about porting the Jam STAPL Player, Jam Byte-Code Player, and other debugging methods, see the readme file that comes with the Jam STAPL Player or Jam Byte-Code Player source code or go to http://www.jamisp.com. |