HT66FV130 Datasheet, PDF (35/259 Pages) Holtek Semiconductor Inc – Enhanced Voice Flash MCU

HT66FV130/HT66FV140
HT66FV150/HT66FV160
Enhanced Voice Flash MCU
Look-up Table
Any location within the Program Memory can be defined as a look-up table where programmers can
store fixed data. To use the look-up table, the table pointer must first be setup by placing the address
of the look up data to be retrieved in the table pointer register, TBLP and TBHP. These registers
define the total address of the look-up table.
After setting up the table pointer, the table data can be retrieved from the Program Memory using the
"TABRD [m]" or "TABRDL [m]" instructions respectively when the memory [m] is located in sector
0. If the memory [m] is located in other sectors, the data can be retrieved from the program memory
using the corresponding extended table read instruction such as "LTABRD [m]" or "LTABRDL [m]"
respectively. When the instruction is executed, the lower order table byte from the Program Memory
will be transferred to the user defined Data Memory register [m] as specified in the instruction. The
higher order table data byte from the Program Memory will be transferred to the TBLH special
register. Any unused bits in this transferred higher order byte will be read as "0".
The accompanying diagram illustrates the addressing data flow of the look-up table.
Lastpage or
T B H P R e g is te r
T B L P R e g is te r
P ro g ra m M e m o ry
D a ta
1 6 b its
R e g is te r T B L H
H ig h B y te
U s e r S e le c te d
R e g is te r
L o w B y te
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 statement. The value at this ORG statement is "0F00H" which refers to the start address of the
last page within the 4K Program Memory of the device. The table pointer low byte register is setup
here to have an initial value of "06H". This will ensure that the first data read from the data table will
be at the Program Memory address "0F06H" 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 page that TBHP pointed if the
"TABRD [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 "TABRD [m] instruction is
executed.
Because the TBLH register is a read/write register and can 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 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. 1.50
35
December 06, 2016