NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
FXTH87ERM
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Reference manual
Rev. 5.0 — 4 February 2019
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from internal memory following a reset with execution beginning at address specified by
the reset pseudo-vector ($DFFE and $DFFF).
5.3 WAIT mode
The WAIT mode is also present like other members of the NXP S08 family members; but
is not normally used by the FXTH87E firmware or typical TPMS applications.
5.4 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 boot loader or user application
program into the FLASH program memory before the MCU is operated in RUN mode
for the first time. When the FXTH87E is shipped from the NXP 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.
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