BS2824 Holtek Semiconductor Inc., BS2824 Datasheet - Page 72

• Manufacturer Part Number: BS2824
• Description: Touch Key Mcu
• Manufacturer: Holtek Semiconductor Inc.

BS2824/BS2854/BS2868
Touch Key MCU
Rev. 1.00
Branches and Control Transfer
Bit Operations
Table Read Operations
Other Operations
from where it can be examined and the necessary serial bit set high or low. Another application
where rotate data operations are used is to implement multiplication and division calculations.
Program branching takes the form of either jumps to specified locations using the JMP instruction or
to a subroutine using the CALL instruction. They differ in the sense that in the case of a subroutine
call, the program must return to the instruction immediately when the subroutine has been carried
out. This is done by placing a return instruction RET in the subroutine which will cause the program
to jump back to the address right after the CALL instruction. In the case of a JMP instruction, the
program simply jumps to the desired location. There is no requirement to jump back to the original
jumping off point as in the case of the CALL instruction. One special and extremely useful set of
branch instructions are the conditional branches. Here a decision is first made regarding the
condition of a certain data memory or individual bits. Depending upon the conditions, the program
will continue with the next instruction or skip over it and jump to the following instruction. These
instructions are the key to decision making and branching within the program perhaps determined
by the condition of certain input switches or by the condition of internal data bits.
The ability to provide single bit operations on Data Memory is an extremely flexible feature of all
Holtek microcontrollers. This feature is especially useful for output port bit programming where
individual bits or port pins can be directly set high or low using either the SET [m].i or CLR
[m].i instructions respectively. The feature removes the need for programmers to first read the 8-bit
output port, manipulate the input data to ensure that other bits are not changed and then output the
port with the correct new data. This read-modify-write process is taken care of automatically when
these bit operation instructions are used.
Data storage is normally implemented by using registers. However, when working with large
amounts of fixed data, the volume involved often makes it inconvenient to store the fixed data in the
Data Memory. To overcome this problem, Holtek microcontrollers allow an area of Program
Memory to be setup as a table where data can be directly stored. A set of easy to use instructions
provides the means by which this fixed data can be referenced and retrieved from the Program
Memory.
In addition to the above functional instructions, a range of other instructions also exist such as the
Watchdog Timer for reliable program operations under extreme electric or electromagnetic
environments. For their relevant operations, refer to the functional related sections.
HALT instruction for Power-down operations and instructions to control the operation of the
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January 27, 2010