Holtek HT48R05A-1, Руководство пользователя, Страница: 22 / 125

Special Vectors
Within the Program Memory, certain locations are reserved for special usage, such as reset and in-
terrupts.
·
Location 000H
This vector is reserved for use by the chip reset for program initialization. After a chip reset is ini-
tiated, the program will jump to this location and begin execution.
·
Location 004H
This vector is used by the external interrupt. If the external interrupt pin on the device receives a
high to low transition, the program will jump to this location and begin execution if the external in-
terrupt is enabled and the stack is not full.
·
Location 008H
This internal interrupt vector is used by the Timer/Event Counter. If a counter overflow occurs,
the program will jump to this location and begin execution if the internal interrupt is enabled and
the stack is not full.
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
lower-order address of the look-up data to be retrieved in the Table Pointer Register TBLP. This
register defines the lower 8-bit address of the look-up table. After setting up the table pointer, the
table data can be retrieved from the current Program Memory page using the
²
TABRDC [m]
²
in-
struction. In the case of the HT48R06A-1/HT48C06, HT48R07A-1/HT48C07, HT48R08A-1/
HT48C08 and HT48R09A-1/HT48C09 devices, the additional
²
TABRDL [m]
²
instruction can be
used to retrieve data from the last page of the Program Memory, however, this instruction is not
valid for the HT48R05A-1/HT48C05 devices. When these instructions are executed, the lower or-
der table byte from the Program Memory will be transferred to the user defined Data Memory regis-
ter [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
²
0
²
.
Chapter 1 Hardware Structure
15
N o t I m p l e m e n t e d
1 F F H
2 0 0 H
3 F F H
H T 4 8 R 0 6 A - 1 / H T 4 8 C 0 6
H T 4 8 R 0 7 A - 1 / H T 4 8 C 0 7
I n i t i a l i z a t i o n
V e c t o r
E x t e r n a l
I n t e r r u p t V e c t o r
T i m e r / C o u n t e r
I n t e r r u p t V e c t o r
E x t e r n a l
I n t e r r u p t V e c t o r
T i m e r / C o u n t e r
I n t e r r u p t V e c t o r
I n i t i a l i z a t i o n
V e c t o r
0 0 8 H
H T 4 8 R 0 5 A - 1 / H T 4 8 C 0 5
0 0 0 H
0 0 4 H
E x t e r n a l
I n t e r r u p t V e c t o r
T i m e r / C o u n t e r
I n t e r r u p t V e c t o r
I n i t i a l i z a t i o n
V e c t o r
1 4 b i t s 1 4 b i t s 1 4 b i t s
7 F F H
H T 4 8 R 0 8 A - 1 / H T 4 8 C 0 8
H T 4 8 R 0 9 A - 1 / H T 4 8 C 0 9