Motorola M68HC11EVBD, User Manual

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HARDWARE PREPARATION AND INSTALLATION
M68HC11EVBU/D 2-5
2.3.2 Program Execution Select Header (J2)
Use jumper header J2 to select whether the BUFFALO monitor prompt is displayed or if a jump
to internal EEPROM is executed. At reset the monitor checks the logic state of the PE0 line. If
PE0 = 0 (a jumper installed on pins 2 and 3 of jumper header J2) the monitor program is
executed and the prompt displayed. If PE0 = 1 (a jumper is installed on pins 1 and 2 of jumper
header J2) the monitor automatically jumps directly to EEPROM (address location $B600) and
executes user program code without monitor intervention.
The EVBU is factory-configured and shipped with a jumper installed on pins 2 and 3 of jumper
header J2 (BUFFALO monitor program execution, shown below). Reconfigure the EVBU by
moving the jumper to pins 1 and 2 of jumper header J2 if you want to jump directly to EEPROM
address $B600 for user code execution.
J2
1
2
3
MONITOR
(LOGIC 0)
EEPROM
(LOGIC 1)
Fabricated Jumper
If you use the PE0 line for A/D operations, the loading condition introduced by jumper header J2
may not be desired. There are two ways to bypass this potential problem.
1. Jumper header J2 is only required at the trailing edge of reset, so you can remove the
fabricated jumper after reset. Using this method, it is possible that your target system
circuitry might drive the PE0 line to the wrong state during reset.
2. Program the first three EEPROM locations with $7E, $E0, and $0A, respectively.
Next, remove installed jumper from jumper header J2. Independent of the level
present on the PE0 line, the BUFFALO monitor will gain control after a reset
operation.
For additional EEPROM jump operation information, described above, refer to EVBU monitor
program (lines 0162 and 0163) of the listing stored on the EVBU diskette (see file buf32.asm).