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HTG12N0 Datasheet(PDF) 10 Page - Holtek Semiconductor Inc |
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HTG12N0 Datasheet(HTML) 10 Page - Holtek Semiconductor Inc |
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10 / 30 page  Data memory – RAM The static data memory (RAM) is arranged in 256 ×4 bit format and is used to store data. All of the data memory locations are indirectly ad- dressable through the register pair R1,R0 or R3,R2; for example MOV A,[R3R2] or MOV [R3R2],A. There are two banks for data memory in HTG12N0, each bank shown in the figure can be switched by the assignment of PC0. Each bank maps to different area of the data memory. There are two areas in the data memory, the temporary data area and the display data area. Access to the temporary data area is from 00H to 7FH of bank 0 and 00H to 7FH of bank 1, Locations 80H to FFH (don’t care the bank pointer) represent the display data area. When data is written into the display data area it is automatically read by the LCD driver which then generates the corresponding LCD driving signals. The relationship between the data pointer RAM locations are shown in the table. Display data area (80H~FFH) don’t care about the PC0. Accumulator – ACC The accumulator is the most important data register in the processor. It is one of the sources of input to the ALU and the destination of the results of the operations performed in the ALU. Data to and from the I/O ports and memory also passes through the accumulator. Arithmetic and logic unit – ALU This circuit performs the following arithmetic and logical operations ... • Add with or without carry • Subtract with or without carry • AND, OR, Exclusive-OR • Rotate right, left through carry • BCD decimal adjust for addition • Increment, decrement • Data transfers • Branch decisions The ALU not only outputs the results of data operations, but also sets the status of the carry flag (CF) in some instructions. Timer/counter The HTG12N0 contains a programmable 8-bit count-up counter which can be used to count external events or as a clock to generate an accurate time base. If the 8-bit timer clock is supplied by an exter- nal source from pin TMCLK, synchronization problems may occur when reading the data from the timer. It is therefore suggested that the timer is stopped before retrieving the data. The 8-bit counter will increment on the rising edge of the clock whether it is internally or externally generated. The timer/counter may be set and read with software instructions and stopped by a hard- ware reset or a TIMER OFF instruction. To restart the timer, load the counter with the value XXH and then issue a TIMER ON in- struction. Note that XX is the desired start count immediate value of the 8 bits. Once the timer/counter is started it increments to a maximum count of FFH and then overflows to zero (00H). It then continues to count until stopped by a TIMER OFF instruction or a reset. The increment from the maximum count of FFH to zero (00H) triggers a timer flag TF and an internal interrupt request. The interrupt Data memory Data memory HTG12N0 10 18th Mar ’99 |
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