ht82k74e Holtek Semiconductor Inc., ht82k74e Datasheet - Page 11

• Manufacturer Part Number: ht82k74e
• Description: 27mhz Keyboard/ Mouse Tx 8-bit Mcu
• Manufacturer: Holtek Semiconductor Inc.

tempreg1
tempreg2
mov
mov
tabrdl
dec
tabrdl
org
dc
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 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.
Rev. 1.00
db
db
:
:
a,06h
tblp,a
:
:
tempreg1
tblp
tempreg2
:
:
700h
00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:
?
?
; temporary register #1
; temporary register #2
; initialise table pointer - note that this address
; is referenced
; to the last page or present page
; transfers value in table referenced by table pointer
; to tempregl
; data at prog. memory address 706H transferred to
; tempreg1 and TBLH
; reduce value of table pointer by one
; transfers value in table referenced by table pointer
; to tempreg2
; data at prog.memory address 705H transferred to
; tempreg2 and TBLH
; in this example the data 1AH is transferred to
; tempreg1 and data 0FH to register tempreg2
; the value 00H will be transferred to the high byte
; register TBLH
; sets initial address of last page
11
HT82K74E/HT82K74EE
December 15, 2009