MC9S08QD4 Datasheet, PDF (166/202 Pages) Freescale Semiconductor, Inc – Microcontrollers

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BDC CLOCK
(TARGET MCU)
HOST DRIVE
TO BKGD PIN
HIGH-IMPEDANCE
TARGET MCU
DRIVE AND
SPEED-UP PULSE
PERCEIVED START
OF BIT TIME
SPEEDUP
PULSE
BKGD PIN
10 CYCLES
10 CYCLES
EARLIEST START
OF NEXT BIT
HOST SAMPLES BKGD PIN
Figure 12-4. BDM Target-to-Host Serial Bit Timing (Logic 0)
12.2.3 BDC Commands
BDC commands are sent serially from a host computer to the BKGD pin of the target HCS08 MCU. All
commands and data are sent MSB-first using a custom BDC communications protocol. Active background
mode commands require that the target MCU is currently in the active background mode while
non-intrusive commands may be issued at any time whether the target MCU is in active background mode
or running a user application program.
Table 12-1 shows all HCS08 BDC commands, a shorthand description of their coding structure, and the
meaning of each command.
Coding Structure Nomenclature
This nomenclature is used in Table 12-1 to describe the coding structure of the BDC commands.
MC9S08QD4 Series MCU Data Sheet, Rev. 3
166
Freescale Semiconductor