mc68hc11d0cfn2 Freescale Semiconductor, Inc, mc68hc11d0cfn2 Datasheet - Page 22

• Manufacturer Part Number: mc68hc11d0cfn2
• Description: M68hc11 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Operating Modes and Memory
2.2.2 Expanded Multiplexed Mode
2.2.3 Special Bootstrap Mode (BOOT)
Data Sheet
22
NOTE:
In the expanded-multiplexed mode, the MCU can address up to 64 Kbytes of
address space. High-order address bits are output on the port B pins. Low-order
address bits and the bidirectional data bus are multiplexed on port C. The AS pin
provides the control output used in demultiplexing the low-order address. The R/W
pin is used to control the direction of data transfer on the port C bus.
If this mode is entered out of reset, the EPROM is located at $7000–$7FFF and
vector accesses are from external memory. To be in expanded-multiplexed mode
with EPROM located at $F000–$FFFF, it is necessary to start in single-chip mode,
executing out of EPROM, and then set the MDA bit of the HPRIO register to switch
mode.
R/W, AS, and the high-order address bus (port B) are inputs in single-chip mode.
These inputs may need to be pulled up so that off-chip accesses cannot occur
while the MCU is in single-chip mode.
This special mode is similar to single-chip mode. The resident bootloader program
contains a 256-byte program in a special on-chip read-only memory (ROM). The
user downloads a small program into on-board RAM using the SCI port. Program
control is passed to RAM when an idle line of at least four characters occurs. In this
mode, all interrupt vectors are mapped to RAM (see
can set up a jump table, if desired.
Bootstrap mode (BOOT) is entered out of reset if the voltage level on both MODA
and MODB is low. The programming aspect of bootstrap mode, used to program
the one-time programmable ROM (OTPROM) through the MCU, is entered
automatically if IRQ is low and programming voltage is available on the V
IRQ should be pulled up while in reset with MODA and MODB configured for
bootstrap mode to prevent unintentional programming of the EPROM.
This versatile mode (BOOT) can be used for test and diagnostic functions on
completed modules and for programming the on-board PROM. The serial receive
logic is initialized by software in the bootloader ROM, which provides program
control for the SCI baud rate and word format. Mode switching to other modes can
occur under program control by writing to the SMOD and MDA bits of the HPRIO
register. Two special bootloader functions allow either an immediate jump-to-RAM
at memory address $0000 or an immediate jump-to-EPROM at $F000.
Freescale Semiconductor, Inc.
For More Information On This Product,
Operating Modes and Memory
Go to: www.freescale.com
Table
2-2), so that the user
MC68HC711D3 — Rev. 2
MOTOROLA
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pin.