mc68hc705p6a Freescale Semiconductor, Inc, mc68hc705p6a Datasheet - Page 27

• Manufacturer Part Number: mc68hc705p6a
• Description: M68hc05 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 3
Operating Modes
3.1 Introduction
The MC68HC705P6A has two modes of operation that affect the pinout and architecture of the MCU:
user mode and bootloader mode. The user mode is normally used for the application and the bootloader
mode is used for programming the EPROM. The conditions required to enter each mode are shown in
Table
the rising edge of the external RESET pin.
The mode of operation is also determined whenever the internal computer operating properly (COP)
watchdog timer resets the MCU. When the COP timer expires, the voltage applied to the IRQ/V
controls the mode of operation while the voltage applied to PD7/TCAP is ignored. The voltage applied to
PD7/TCAP during the last rising edge on RESET is stored in a latch and used to determine the mode of
operation when the COP watchdog timer resets the MCU.
3.2 User Mode
The user mode allows the MCU to function as a self-contained microcontroller, with maximum use of the
pins for on-chip peripheral functions. All address and data activity occurs within the MCU and are not
available externally. User mode is entered on the rising edge of RESET if the IRQ/V
normal operating voltage range. The pinout for the user mode is shown in
In the user mode, there is an 8-bit I/O port, a second 8-bit I/O port shared with the analog-to-digital (A/D)
subsystem, one 3-bit I/O port shared with the serial input/output port (SIOP), and a 3-bit port shared with
the 16-bit timer subsystem, which includes one general-purpose I/O pin.
3.3 Bootloader Mode
The bootloader mode provides a means to program the user EPROM from an external memory device or
host computer. This mode is entered on the rising edge of RESET if V
V
in the same address space it will occupy in the internal MCU EPROM, including the mask option register
(MOR) at $1EFF and $1F00.
Freescale Semiconductor
DD
is applied to the PD7/TCAP pin. The user code in the external memory device must have data located
3-1. The mode of operation is determined by the voltages on the IRQ/V
RESET Pin
Table 3-1. Operating Mode Conditions After Reset
MC68HC705P6A Advance Information Data Sheet, Rev. 2.1
V
IRQ/V
SS
V
to V
PP
PP
DD
PD7/TCAP
V
SS
V
to V
DD
DD
PP
is applied to the IRQ/V
Figure
Single chip
Bootloader
PP
Mode
and PD7/TCAP pins on
3-1.
PP
pin is within the
PP
PP
pin and
pin
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