HT46R74D-1 Holtek Semiconductor, HT46R74D-1 Datasheet - Page 8

• Manufacturer Part Number: HT46R74D-1
• Description: Dual Slope A/D Type MCU
• Manufacturer: Holtek Semiconductor

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When a control transfer takes place, an additional
dummy cycle is required.
Program Memory - ROM
The program memory is used to store the program in-
structions which are to be executed. It also contains
data, table, and interrupt entries, and is organized with a
structure of 4096 15 bits which are addressed by the
program counter and table pointer.
Certain locations in the ROM are reserved for special
usage:
Note:
Rev. 1.10
TABRDC [m]
TABRDL [m]
Location 000H
Location 000H is reserved for program initialization.
After a chip reset, the program always begins execu-
tion at this location.
Location 004H
Location 004H is reserved for the INT0 external inter-
rupt service program. If the INT0 input pin is activated,
and the interrupt is enabled, and the stack is not full,
the program begins execution at location 004H.
Location 008H
Location 008H is reserved for the INT1 external inter-
rupt service program. If the INT1 input pin is activated,
and the interrupt is enabled, and the stack is not full,
the program begins execution at location 008H.
Location 00CH
Instruction(s)
*11~*0: Table location bits
@7~@0: Table pointer bits
Program Memory
P11
*11
1
P10
*10
1
P9
*9
1
P8
*8
1
Table Location
@7
@7
*7
8
Table Location
Stack Register - STACK
The stack register is a special part of the memory used
to save the contents of the program counter. The stack
is organized into 6 levels and is neither part of the data
nor part of the program, and is neither readable nor
writeable. Its activated level is indexed by a stack
pointer, SP, and is neither readable nor writeable. At the
start of a subroutine call or an interrupt acknowledg-
P11~P8: Current program counter bits
@6
@6
Location 00CH is reserved for the Timer/Event Coun-
ter 0 interrupt service program. If a timer interrupt re-
sults from a Timer/Event Counter 0 overflow, and if the
interrupt is enabled and the stack is not full, the pro-
gram begins execution at location 00CH.
Location 010H
Location 010H is reserved for the Timer/Event Coun-
ter 1 interrupt service program. If a timer interrupt re-
sults from a Timer/Event Counter 1 overflow, and if the
interrupt is enabled and the stack is not full, the pro-
gram begins execution at location 010H.
Location 014H
Location 014H is reserved for the ADC interrupt ser-
vice program. If an ADC interrupt occurs, and the in-
terrupt is enabled, and the stack is not full, the
program begins execution at location 014H.
Location 018H
Location 018H is reserved for the real time clock inter-
rupt service program. If a real time clock interrupt oc-
curs, and the interrupt is enabled, and the stack is not
full, the program begins execution at location 018H.
Table location
Any location in the Program Memory can be used as a
look-up table. The instructions TABRDC [m] (the
current page, 1 page=256 words) and TABRDL [m]
(the last page) transfer the contents of the lower-order
byte to the specified data memory, and the contents of
the higher-order byte to the TBLH register, which is
the Table high order byte register. Only the destination
of the lower-order byte in the table is well-defined; the
other bits of the table word are all transferred to the
lower portion of TBLH. The TBLH register is read only,
and the table pointer, TBLP, is a read/write register,
and is used to indicate the table location. Before ac-
cessing the table, the location should be placed into
the TBLP register. All the table related instructions re-
quire 2 cycles to complete their operation. These ar-
eas may function as normal ROM depending upon the
user s requirements.
*6
@5
@5
*5
@4
@4
*4
@3
@3
*3
@2
@2
*2
HT46R74D-1
January 11, 2007
@1
@1
*1
@0
@0
*0