
Application Note
AN1060 — Rev. 1.0
226
MOTOROLA
series resistor will prevent direct conflict between the internal TxD driver 
and the external driver connected to PD1 through the series resistor. 
Other
The bootloader firmware sets the DWOM control bit, which configures all 
port D pins for wire-OR operation. During the bootloading process, all 
port D pins except the PD1/TxD pin are configured as high-impedance 
inputs. Any port D pin that normally is used as an output should have a 
pullup resistor so it does not float during the bootloading process. 
Driving Boot Mode from Another M68HC11 
A second M68HC11 system can easily act as the host to drive bootstrap 
loading of an M68HC11 MCU. This method is used to examine and 
program non-volatile memories in target M68HC11s in Motorola EVMs. 
The following hardware and software example will demonstrate this and 
other bootstrap mode features. 
The schematic in 
Figure 6
 shows the circuitry for a simple EPROM 
duplicator for the MC68HC711E9. The circuitry is built in the wire-wrap 
area of an M68HC11EVBU evaluation board to simplify construction. 
The schematic shows only the important portions of the EVBU circuitry 
to avoid confusion. To see the complete EVBU schematic, refer to the 
M68HC11EVBU Universal Evaluation Board User’s Manual
, Motorola 
document order number M68HC11EVBU/D. 
The default configuration of the EVBU must be changed to make the 
appropriate connections to the circuitry in the wire-wrap area and to 
configure the master MCU for bootstrap mode. A fabricated jumper must 
be installed at J6 to connect the XTAL output of the master MCU to the 
wire-wrap connector P5, which has been wired to the EXTAL input of the 
target MCU. Cut traces that short across J8 and J9 must be cut on the 
solder side of the printed circuit board to disconnect the normal SCI 
connections to the RS232 level translator (U4) of the EVBU. The J8 and 
J9 connections can be restored easily at a later time by installing 
fabricated jumpers on the component side of the board. A fabricated 
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