D-Bug12 Customization Data
Customization Data Area
M68HC12A4EVB Evaluation Board — Rev. 1
User’s Manual
MOTOROLA
D-Bug12 Customization Data
137
D.2.4 SysClk Field
The
SysClk
field is used to inform D-Bug12 of the system clock frequency,
M. Its value, in hertz, is set to 8,000,000. The E-clock frequency is the same as
the system clock frequency, M.
SysClk
is used by the D-Bug12 BAUD
command in calculating the new value of the SCI baud register for the requested
baud rate.
NOTE:
It is the responsibility of the startup code to perform any actions necessary to
set the system clock frequency. D-Bug12 does not set or change the system clock
frequency using the
SysClk
value.
D.2.5 IOBase Field
The
IOBase
field defines the base address of the input/output (I/O) registers.
This address is used by D-Bug12 when accessing the I/O registers associated
with the SCI and when programming or erasing the on-chip EEPROM. On the
MC68HC812A4, the I/O registers are mappable to any 2-Kbyte memory space.
Therefore, the
IOBase
entry should be only a multiple of 2048. The value of
IOBase
is set to 0x0000 which is the default address of the I/O registers for the
MC68HC812A4.
NOTE:
It is the responsibility of the startup code to set the base address of the I/O
registers. D-Bug12 does not set or change the I/O register base address.
D.2.6 SCIBaudRegVal Field
The
SCIBaudRegVal
field is used to set the initial baud rate of the SCI used
for console I/O by D-Bug12. Note that the value in
SCIBaudRegVal
is
written directly to the baud register of the console SCI. The value is not the
desired baud rate. The calculation of this value is not made by D-Bug12 because
of the possibility of an invalid baud register value. Without a valid baud register
value during SCI initialization, D-Bug12 would have no way to inform the user
that a problem existed. Not all combinations of baud rates and system clock
frequencies produce a valid baud register value. The formula used to calculate
the baud register value is:
BaudRegVal = MCLK ( 16 * SCIBaudRate)
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Freescale Semiconductor, Inc.
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