HT46R005 datasheet(15/62 Pages) HOLTEK

15 / 62 page

HT48R005/HT46R005

Rev. 1.00

November 29, 2011

The following diagram illustrates the addressing/data

flow of the look-up table:

Table Program Example

The accompanying example shows how the table

pointer and table data is defined and retrieved from the

device. This example uses raw table data located in the

last page which is stored there using the ORG state-

ment. 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 ad-

dress

²106H² or 6 locations after the start of the last

page. Note that the value for the table pointer is refer-

enced to the first address of the present page if the

²TABRDC [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

²TABRDL [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 the table read instructions. If using the table

read instructions, the Interrupt Service Routines may

change the value of TBLH and subsequently cause er-

rors if used again by the main routine. As a rule it is rec-

ommended that simultaneous use of the table read

instructions should be avoided. However, in situations

where simultaneous use cannot be avoided, the inter-

rupts 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.

Instruction

Table Location Bits

TABRDC [m]

PC9

PC8

TABRDL [m]

Table Location

Note:

PC9~PC8: Current program Counter bits

@7~@0: Table Pointer TBLP bits

· Table Read Program Example - 0.5K ROM size

tempreg1 db ?

; temporary register #1

tempreg2 db ?

; temporary register #2

mov a,06h

; initialise table pointer - note that this address is referenced

mov tblp,a

; to the last page or present page

tabrdl

tempreg1

; transfers value in table referenced by table pointer to tempregl

; data at prog. memory address

²106H² transferred to tempreg1 and TBLH

dec tblp

; reduce value of table pointer by one

tabrdl

tempreg2

; transfers value in table referenced by table pointer to tempreg2

; data at prog.memory address

²105H² transferred to tempreg2 and TBLH

; in this example the data

²1AH² is transferred to

; tempreg1 and data

²0FH² to register tempreg2

; the value

²00H² will be transferred to the high byte register TBLH

org 100h

; sets initial address of last page

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

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

L a s t p a g e o r

p r e s e n t p a g e

P C x ~ P C 8

P C H i g h B y t e

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

D a t a

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

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