BS85B12-3 HOLTEK [Holtek Semiconductor Inc], BS85B12-3 Datasheet - Page 68

• Manufacturer Part Number: BS85B12-3
• Description: Touch Key Flash Type 8-Bit MCU with LCD/LED Driver
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Rev. 1.00
Programming Considerations
The TM Counter Registers and the Capture/Compare CCRA and CCRB 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 CCRB 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 CCRB low byte registers, named TMxAL and
TMxBL, using the following access procedures. Accessing the CCRA or CCRB low byte registers
without following these access procedures will result in unpredictable values.
The following steps show the read and write procedures:
Writing Data to CCRB or CCRA
Reading Data from the Counter Registers and CCRB or CCRA
Step 1. Write data to Low Byte TMxAL or TMxBL
- note that here data is only written to the 8-bit buffer.
Step 2. Write data to High Byte TMxAH or TMxBH
- here data is written directly to the high byte registers and simultaneously data is latched from
Step 1. Read data from the High Byte TMxDH, TMxAH or TMxBH
- here data is read directly from the High Byte registers and simultaneously data is latched from
Step 2. Read data from the Low Byte TMxDL, TMxAL or TMxBL
- this step reads data from the 8-bit buffer.
the 8-bit buffer to the Low Byte registers.
the Low Byte register into the 8-bit buffer.
Touch Key Flash MCU with LCD/LED Driver
TM Counter Register (Read only)
TM CCRA Register (Read/Write)
TM CCRB Register (Read/Write)
TMxDL
TMxAL
TMxBL
Buffer
8-bit
TMxDH
TMxAH
TMxBH
62
BS85B12-3/BS85C20-3
Data
Bus
February 1, 2011