HT46R49 Holtek Semiconductor, HT46R49 Datasheet - Page 12

• Manufacturer Part Number: HT46R49
• Description: Cost-Effective A/D Type 8-Bit MCU
• Manufacturer: Holtek Semiconductor

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tempreg1 db
tempreg2 db
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 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.
Note:
Rev. 1.30
TABRDC [m] PC11
TABRDL [m]
Instruction
:
:
PC11~PC8: Current Program Counter bits
@7~@0: Table Pointer TBLP bits
For the HT46R49 the Table address location is 12 bits, i.e. from b11~b0.
For the HT46R47 and HT46R48A, the Table address location is 11 bits, i.e. from b10~b0.
For the HT46R46, the Table address location is 10 bits, i.e. from b9~b0.
a,06h
tblp,a
:
:
tempreg1
tblp
tempreg2
:
:
700h
00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:
b11
1
?
?
PC10
b10
1
; 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 (for HT46R47)
PC9
b9
1
PC8
b8
1
Table Location
@7
@7
b7
HT46R46/C46/R47/C47/R48A/C48A/R49
Table Location Bits
12
@6
@6
b6
Data Memory
The Data Memory is a volatile area of 8-bit wide RAM
internal memory and is the location where temporary in-
formation is stored. Divided into two sections, the first of
these is an area of RAM where special function registers
are located. These registers have fixed locations and
are necessary for correct operation of the device. Many
of these registers can be read from and written to di-
rectly under program control, however, some remain
protected from user manipulation. The second area of
Data Memory is reserved for general purpose use. All
locations within this area are read and write accessible
under program control.
@5
@5
b5
@4
@4
b4
@3
@3
b3
@2
@2
b2
@1
@1
b1
June 5, 2008
@0
@0
b0