HT56R66(2009) Просмотр технического описания (PDF) - Holtek Semiconductor
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HT56R66 Datasheet PDF : 104 Pages
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HT56R66/HT56R666
Table Program Example
The following example shows how the table pointer and
table data is defined and retrieved from the HT56R666.
This example uses raw table data located in the last
page which is stored there using the ORG statement.
The value at this ORG statement is ²3F00H² which re-
fers to the start address of the last page within the 16K
Program Memory of the HT56R666 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
²3F06H² 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 trans-
ferred 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 ²3F06H² transferred to
; tempreg1 and TBLH
; reduce value of table pointer by one
tabrdl tempreg2
:
:
org 3F00h
; transfers value in table referenced by table pointer
; to tempreg2
; data at prog.memory address ²3F05H² 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. 1.10
19
September 8, 2009
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