HT56R688 Просмотр технического описания (PDF) - Holtek Semiconductor
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HT56R688 Datasheet PDF : 104 Pages
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HT56R67/HT56R668/HT56C668/HT56R678/HT56C678/HT56R688
Table Program Example
The following example shows how the table pointer and
table data is defined and retrieved from the HT56R678/
HT56C678. This example uses raw table data located in
the last page which is stored there using the ORG state-
ment. The value at this ORG statement is ²7F00H²
which refers to the start address of the last page within
the 32K Program Memory of the HT56R678/HT56C678
microcontroller. 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 ²7F06H² 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 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 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 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.
tempreg1 db ?
tempreg2 db ?
:
:
mov a,06h
; temporary register #1
; temporary register #2
; initialise table pointer - note that this address
; is referenced
mov tblp,a
:
:
tabrdl tempreg1
dec tblp
; to the last page or present page
; transfers value in table referenced by table pointer
; to tempregl
; data at prog. memory address ²7F06H² transferred to
; tempreg1 and TBLH
; reduce value of table pointer by one
tabrdl tempreg2
:
:
org 7F00h
; transfers value in table referenced by table pointer
; to tempreg2
; data at prog.memory address ²7F05H² 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
; sets initial address of last page
dc 00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:
Rev. 1.60
18
May 21, 2012
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