MC68HC711E20CFN4 Freescale Semiconductor, MC68HC711E20CFN4 Datasheet - Page 194

• Manufacturer Part Number: MC68HC711E20CFN4
• Description: IC MCU 20K OTP 4MHZ 52-PLCC
• Manufacturer: Freescale Semiconductor
• Series: HC11r

Specifications of MC68HC711E20CFN4

• Core Processor: HC11
• Core Size: 8-Bit
• Speed: 4MHz
• 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

Basic Bootstrap Mode
Basic Bootstrap Mode
This section describes only basic functions of the bootstrap mode. Other functions of the bootstrap mode
are described in detail in the remainder of this application note.
When an M68HC11 is reset in bootstrap mode, the reset vector is fetched from a small internal read-only
memory (ROM) called the bootstrap ROM or boot ROM. The firmware program in this boot ROM then
controls the bootloading process, in this manner:
Bootstrap mode is useful both at the component level and after the MCU has been embedded into a
finished user system.
At the component level, Freescale uses bootstrap mode to control a monitored burn-in program for the
on-chip electrically erasable programmable read-only memory (EEPROM). Units to be tested are loaded
into special circuit boards that each hold many MCUS. These boards are then placed in burn-in ovens.
Driver boards outside the ovens download an EEPROM exercise and diagnostic program to all MCUs in
parallel. The MCUs under test independently exercise their internal EEPROM and monitor programming
and erase operations. This technique could be utilized by an end user to load program information into
the EPROM or EEPROM of an M68HC11 before it is installed into an end product. As in the burn-in setup,
many M68HC11s can be gang programmed in parallel. This technique can also be used to program the
EPROM of finished products after final assembly.
Freescale also uses bootstrap mode for programming target devices on the M68HC11 evaluation
modules (EVM). Because bootstrap mode is a privileged mode like special test, the EEPROM-based
configuration register (CONFIG) can be programmed using bootstrap mode on the EVM.
The greatest benefits from bootstrap mode are realized by designing the finished system so that bootstrap
mode can be used after final assembly. The finished system need not be a single-chip mode application
for the bootstrap mode to be useful because the expansion bus can be enabled after resetting the MCU
in bootstrap mode. Allowing this capability requires almost no hardware or design cost and the addition
of this capability is invisible in the end product until it is needed.
The ability to control the embedded processor through downloaded programs is achieved without the
disassembly and chip-swapping usually associated with such control. This mode provides an easy way
to load non-volatile memories such as EEPROM with calibration tables or to program the application
firmware into a one-time programmable (OTP) MCU after final assembly.
Another powerful use of bootstrap mode in a finished assembly is for final test. Short programs can be
downloaded to check parts of the system, including components and circuitry external to the embedded
MCU. If any problems appear during product development, diagnostic programs can be downloaded to
find the problems, and corrected routines can be downloaded and checked before incorporating them into
the main application program.
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First, the on-chip SCI (serial communications interface) is initialized. The first character received
($FF) determines which of two possible baud rates should be used for the remaining characters in
the download operation.
Next, a binary program is received by the SCI system and is stored in RAM.
Finally, a jump instruction is executed to pass control from the bootloader firmware to the user’s
loaded program.
M68HC11 Bootstrap Mode, Rev. 1.1
Freescale Semiconductor