HT66F13 datasheet(22/173 Pages) HOLTEK

22 / 173 page

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

TableProgramExample

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

²700H² which refers to the start

address of the last page within the 2K Program Memory of the HT66F14. The table pointer is setup

here to have an initial value of

²06H². This will ensure that the first data read from the data table will be

at the Program Memory address

²706H² 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

²TABRD [m]²

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

²TABRD [m]² 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.

TableReadProgramExample

tempreg1

db ?

; temporary register #1

tempreg2

db ?

; temporary register #2

mov

a,06h

; initialise low table pointer - note that this address

mov

tblp,a

; is referenced

mov

a,07h

; initialise high table pointer

mov

tbhp,a

tabrd tempreg1

; transfers value in table referenced by table pointer data at

; program memory address

²706H² transferred to tempreg1 and TBLH

dec tblp

; reduce value of table pointer by one

tabrd tempreg2

; transfers value in table referenced by table pointer data at

; program memory address

²705H² transferred to tempreg2 and TBLH

; in this example the data

²1AH² is transferred to tempreg1 and

; data

²0FH² to register tempreg2

org 700h

; sets initial address of program memory

dc 00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh

HT66F13/HT66F14/HT66F15

EnhancedA/DFlashType MCU

Rev.1.10

February9,2011

R e g i s t e r T B L H

U s e r S e l e c t e d

R e g i s t e r

H i g h B y t e

L o w B y t e

T B L P R e g i s t e r

D a t a

1 4 ~ 1 5 b i t s

P r o g r a m M e m o r y

L a s t p a g e o r

T B H P R e g i s t e r

HT66F13 Datasheet(PDF) 22 Page - Holtek Semiconductor Inc

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