MC68HC711E20CFN2 Freescale Semiconductor, MC68HC711E20CFN2 Datasheet - Page 297

• Manufacturer Part Number: MC68HC711E20CFN2
• Description: IC MCU 20K 2MHZ OTP 52-PLCC
• Manufacturer: Freescale Semiconductor
• Series: HC11r

Specifications of MC68HC711E20CFN2

• Core Processor: HC11
• Core Size: 8-Bit
• Speed: 2MHz
• Connectivity: SCI, SPI
• Peripherals: POR, WDT
• Number Of I /o: 38
• Program Memory Size: 20KB (20K x 8)
• Program Memory Type: OTP
• Eeprom Size: 512 x 8
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 52-PLCC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AN1060 — Rev. 1.0
MOTOROLA
The duplicator program in EEPROM clears the DWOM control bit to
change port D (thus, TxD) of U3 to normal driven outputs. This
configuration will prevent interference due to R9 when TxD from the
target MCU (U6) becomes active. Series resistor R9 demonstrates how
TxD of U3 can drive RxD of U3[1] and later TxD of U6 can drive RxD of
U3 without a destructive conflict between the TxD output buffers.
As the target MCU (U6) leaves reset, its mode pins select bootstrap
mode so the bootloader firmware begins executing. A break is sent out
the TxD pin of U6. At this time, the TxD pin of U3 is at a driven high so
R9 acts as a pullup resistor for TxD of the target MCU (U6). The break
character sent from U6 is received by U3 so the duplicator program that
is running in the EEPROM of the master MCU knows that the target
MCU is ready to accept a bootloaded program.
The master MCU sends a leading $FF character to set the baud rate in
the target MCU. Next, the master MCU passes a 3-instruction program
to the target MCU and pauses so the bootstrap program in the target
MCU will stop the loading process and jump to the start of the
downloaded program. This sequence demonstrates the variable-length
download feature of the MC68HC711E9 bootloader.
The short program downloaded to the target MCU clears the DWOM bit
to change its TxD pin to a normal driven CMOS output and jumps to the
EPROM programming utility in the bootstrap ROM of the target MCU.
Note that the small downloaded program did not have to set up the SCI
or initialize any parameters for the EPROM programming process. The
bootstrap software that ran prior to the loaded program left the SCI
turned on and configured in a way that was compatible with the SCI in
the master MCU (the duplicator program in the master MCU also did not
have to set up the SCI for the same reason). The programming time and
starting address for EPROM programming in the target MCU were also
set to default values by the bootloader software before jumping to the
start of the downloaded program.
Before the EPROM in the target MCU can be programmed, the V
power supply must be available at the XIRQ/V
The duplicator program running in the master MCU monitors this voltage
(for presence or absence, not level) at PE7 through resistor divider
PPE
pin of the target MCU.
Application Note
PP
297