HT46801N-1 Holtek Semiconductor, HT46801N-1 Datasheet - Page 14

• Manufacturer Part Number: HT46801N-1
• Description: (HT4xR01x-1) Small Package 8-Bit OTP MCU
• Manufacturer: Holtek Semiconductor

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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 value at this ORG statement is 300H which
refers to the start address of the last page within the 1K
Program Memory of the device. The table pointer is
setup here to have an initial value of 06H . This will en-
sure that the first data read from the data table will be at
Note:
tempreg1 db ?
tempreg2 db ?
mov a,06h
mov tblp,a
tabrdl
dec tblp
tabrdl
org 300h
dc
Rev.1.00
TABRDC [m]
TABRDL [m]
Table Read Program Example - 1K ROM size
Instruction
:
:
:
:
:
:
00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:
PC9~PC8: Current program Counter bits
@7~@0: Table Pointer TBLP bits
tempreg1
tempreg2
PC9
b9
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 306H 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 305H 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
PC8
b8
1
@7
@7
b7
Table Location
@6
@6
b6
14
Table Location Bits
@5
@5
the Program Memory address 306H or 6 locations af-
ter 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 TABRDC [m] 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 TABRDL [m] instruction is ex-
ecuted.
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.
b5
@4
@4
b4
HT46R01B-1/HT46R01N-1
HT48R01B-1/HT48R01N-1
@3
@3
b3
@2
@2
b2
@1
@1
b1
June 9, 2011
@0
@0
b0
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