NXP Semiconductors FXTH870 D Series, Руководство пользователя

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FXTH870xD
Sensors
Freescale Semiconductor, Inc.
11
3 Modes of Operation
The operating modes of the FXTH870xD are described in this section. Entry into each mode, exit from each mode, and
functionality while in each of the modes are described.
3.1 Features
• ACTIVE BACKGROUND DEBUG mode for code development
• STOP modes:
— System clocks stopped
— STOP1: Power down of most internal circuits, including RAM, for maximum power savings; voltage regulator in
standby
— STOP4: All internal circuits powered and full voltage regulation maintained for fastest recovery
3.2 RUN Mode
This is the normal operating mode for the FXTH870xD. This mode is selected when the BKGD/PTA4 pin is high at the rising edge
of reset. In this mode, the CPU executes code from internal memory following a reset with execution beginning at address
specified by the reset pseudo-vector ($DFFE and $DFFF).
3.3 WAIT Mode
The WAIT mode is also present like other members of the Freescale S08 family members; but is not normally used by the
FXTH870xD firmware or typical TPMS applications.
3.4 ACTIVE BACKGROUND Mode
The ACTIVE BACKGROUND mode functions are managed through the BACKGROUND DEBUG controller (BDC) in the HCS08
core. The BDC provides the means for analyzing MCU operation during software development.
ACTIVE BACKGROUND mode is entered in any of four ways:
• When the BKGD/PTA4 pin is low at the rising edge of a power up reset
• When a BACKGROUND command is received through the BKGD/PTA4 pin
• When a BGND instruction is executed by the CPU
• When encountering a BDC breakpoint
Once in ACTIVE BACKGROUND mode, the CPU is held in a suspended state waiting for serial BACKGROUND commands
rather than executing instructions from the user’s application program. Background commands are of two types:
• Non-intrusive commands, defined as commands that can be issued while the user program is running. Non-intrusive
commands can be issued through the BKGD/PTA4 pin while the MCU is in RUN mode; non-intrusive commands can also
be executed when the MCU is in the ACTIVE BACKGROUND mode. Non-intrusive commands include:
— Memory access commands
— Memory-access-with-status commands
— BDC register access commands
— The BACKGROUND command
• ACTIVE BACKGROUND commands, which can only be executed while the MCU is in ACTIVE BACKGROUND mode.
ACTIVE BACKGROUND commands include commands to:
— Read or write CPU registers
— Trace one user program instruction at a time
— Leave ACTIVE BACKGROUND mode to return to the user’s application program (GO)
The ACTIVE BACKGROUND mode is used to program a bootloader or user application program into the FLASH program
memory before the MCU is operated in RUN mode for the first time. When the FXTH870xD is shipped from the Freescale factory,
the FLASH program memory is erased by default (unless specifically requested otherwise) so there is no program that could be
executed in RUN mode until the FLASH memory is initially programmed.
The ACTIVE BACKGROUND mode can also be used to erase and reprogram the FLASH memory after it has been previously
programmed.