mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 1310

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Functional Description
50.4.1.5.24 WRITE_CSR3_BYTE
Write the most significant byte of CSR3 (CSR3[31–24]). This command can be executed
in any mode.
50.4.1.5.25 BDM Accesses of the MAC Registers
The presence of rounding logic in the output datapath of the MAC requires special care
for BDM-initiated reads and writes of its programming model. In particular, any result
rounding modes must be disabled during the read/write process so the exact bit-wise
MAC register contents are accessed.
For example, a BDM read of the accumulator (ACC) must be preceded by two
commands accessing the MAC status register, as shown in the following sequence:
BdmReadACC (
)
Likewise, to write an accumulator register, the following BDM sequence is needed:
BdmWriteACC (
For more information on saving and restoring the complete MAC programming model,
see <<create reference to "Saving and Restoring the EMAC Programming Model"
section>>.
1310
rcreg
wcreg
rcreg
wcreg
rcreg
wcreg
wcreg
wcreg
Write CSR3 Status Byte
macsr;
#0,macsr;
ACC;
#saved_data,macsr; // restore the original macsr
macsr;
#0,macsr;
#data,ACC;
#saved_data,macsr; // restore the original macsr
host
target
0x0F
MCF51JF128 Reference Manual, Rev. 2, 03/2011
CSR3 Data
[31-24]
host
target
// read current macsr contents and save
// disable all rounding modes
// read the desired accumulator
// read current macsr contents and save
// disable all rounding modes
// write the desired accumulator
Preliminary
Always Available
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