Rev. 1.50
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Rev. 1.50
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HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
Programming Considerations
The TM Counter Registers and the Capture/Compare CCRA and CCRP registers, being either 10-
bit or 16-bit, all have a low and high byte structure. The high bytes can be directly accessed, but as
the low bytes can only be accessed via an internal 8-bit buffer, reading or writing to these register
pairs must be carried out in a specific way. The important point to note is that data transfer to and
from the 8-bit buffer and its related low byte only takes place when a write or read operation to its
corresponding high byte is executed.
As the CCRA and CCRP registers are implemented in the way shown in the following diagram and
accessing these register pairs is carried out in a specific way as described above, it is recommended
to use the “MOV” instruction to access the CCRA and CCRP low byte registers, named TMnAL and
TMnRPL, using the following access procedures. Accessing the CCRA or CCRP low byte registers
without following these access procedures will result in unpredictable values.
Data B�s
�-bit B�ffer
TMnDH
TMnDL
TMn�H
TMn�L
TMn Co�nter Re�ister (Read only)
TMn CCR� Re�ister (Read/Write)
TMnRPH
TMnRPL
PTM CCRP Re�ister (Read/Write)
The following steps show the read and write procedures:
• Writing Data to CCRA or CCRP
♦
Step 1. Write data to Low Byte TMnAL or TMnRPL
– note that here data is only written to the 8-bit buffer.
♦
Step 2. Write data to High Byte TMnAH or TMnRPH
– here data is written directly to the high byte registers and simultaneously data is latched
from the 8-bit buffer to the Low Byte registers.
• Reading Data from the Counter Registers and CCRA or CCRP
♦
Step 1. Read data from the High Byte TMnDH, TMnAH or TMnRPH
– here data is read directly from the High Byte registers and simultaneously data is latched
from the Low Byte register into the 8-bit buffer.
♦
Step 2. Read data from the Low Byte TMnDL, TMnAL or TMnRPL
– this step reads data from the 8-bit buffer.
