HT67F60 datasheet(35/242 Pages) HOLTEK

35 / 242 page

HT67F30/HT67F40/HT67F50/HT67F60

TinyPowerTM A/D Flash Type 8-Bit MCU with LCD & EEPROM

Rev. 1.50

March 06 , 2012

Rev. 1.50

March 06 , 2012

Look-up Table

Any location within the Program Memory can be defined as a look-up table where programmers can

store fixed data. To use the look-up table, the table pointer must first be setup by placing the address

of the look up data to be retrieved in the table pointer register, TBLP and TBHP. These registers

define the total address of the look-up table.

After setting up the table pointer, the table data can be retrieved from the Program Memory using

the ”TABRD[m]” or ”TABRDL[m]” instructions, respectively. When the instruction is executed, the

lower order table byte from the Program Memory will be transferred to the user defined Data

Memory register [m] as specified in the instruction. The higher order table data byte from the

Program Memory will be transferred to the TBLH special register. Any unused bits in this

transferred higher order byte will be read as0.

The accompanying diagram illustrates the addressing data flow of the look-up table.

R egi st er T BL H

Us er S el ec te d

R egi st er

Hi gh By te

Low B yt e

TB LP R egi st er

Da ta

15~ 16 bi ts

Pr og ra m Me mo ry

Las t page or

TB HP R eg is te r

Table Program Example

The following example shows how the table pointer and table data is defined and retrieved from the

microcontroller. This example uses raw table data located in the Program Memory which is stored

there using the ORG statement. The value at this ORG statement is “700H” which refers to the start

address of the last page within the 2K Program Memory of the HT67F30. The table pointer is setup

here to have an initial value of “06H”. This will ensure that the first data read from the data table

will be at the Program Memory address “706H” or 6 locations after the start of the last page. Note

that the value for the table pointer is referenced to the first address of the present page if the

“TABRD [m]” instruction is being used. The high byte of the table data which in this case is equal

to zero will be transferred to the TBLH register automatically when the “TABRD [m]” instruction is

executed.

Because the TBLH register is a read-only register and cannot be restored, care should be taken to

ensure its protection if both the main routine and Interrupt Service Routine use table read

instructions. If using the table read instructions, the Interrupt Service Routines may change the value

of the TBLH and subsequently cause errors if used again by the main routine. As a rule it is

recommended that simultaneous use of the table read instructions should be avoided. However, in

situations where simultaneous use cannot be avoided, the interrupts should be disabled prior to the

execution of any main routine table-read instructions. Note that all table related instructions require

two instruction cycles to complete their operation.

In Circuit Programming

The provision of Flash type Program Memory provides the user with a means of convenient and

easy upgrades and modifications to their programs on the same device. As an additional

convenience, Holtek has provided a means of programming the microcontroller in-circuit using a

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