HT82K94A HOLTEK [Holtek Semiconductor Inc], HT82K94A Datasheet - Page 7

• Manufacturer Part Number: HT82K94A
• Description: USB Multimedia Keyboard Encoder 8-Bit MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

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 into
4096 15 bits, addressed by the program counter and ta-
ble pointer.
Certain locations in the program memory are reserved
for special usage:
Note: *12~*0: Table location bits
Rev. 1.00
TABRDC [m]
TABRDL [m]
Location 000H
This area is reserved for program initialization. After
chip reset, the program always begins execution at lo-
cation 000H.
Location 004H
This area is reserved for the USB and external inter-
rupt service program. If the USB interrupt or PA4/EXT
is activated, the interrupt is enabled and the stack is
not full, the program begins execution at location
004H.
There are EXTIF bit in register USR to indicate the ex-
ternal interrupt is activated.
Location 008H
This area is reserved for the Timer/Event Counter 0 in-
terrupt service program. If a timer interrupt results
from a Timer/Event Counter 0 overflow, and if the in-
terrupt is enabled and the stack is not full, the program
begins execution at location 008H.
Instruction
@7~@0: Table pointer bits
Program Memory
P12
*12
1
P11
*11
1
P10
*10
1
P9
*9
1
P8
*8
Table Location
1
P12~P8: Current program counter bits when TBHP is disabled
@7
@7
7
*7
Table Location
TBHP register bit3~bit0 when TBHP is enabled
Location 00CH
This location is reserved for the Timer/Event Counter
1 interrupt service program. If a timer interrupt results
from a Timer/Event Counter 1 overflow, and the inter-
rupt is enabled and the stack is not full, the program
begins execution at location 00CH.
Table location
Any location in the program memory can be used as
look-up tables. There are three method to read the
ROM data by two table read instructions: TABRDC
and
lower-order byte to the specified data memory, and
the higher-order byte to TBLH (08H).
The three methods are shown as follows:
Only the destination of the lower-order byte in the ta-
ble is well-defined, the other bits of the table word are
transferred to the lower portion of TBLH, and the re-
maining 1-bit words are read as 0 . The Table
Higher-order byte register (TBLH) is read only. The ta-
ble pointer (TBLP, TBHP) is a read/write register (07H,
1FH), which indicates the table location. Before ac-
cessing the table, the location must be placed in the
TBLP and TBHP (If the OTP option TBHP is disabled,
the value in TBHP has no effect). The TBLH is read
only and cannot be restored. If the main routine and
the ISR (Interrupt Service Routine) both employ the
table read instruction, the contents of the TBLH in the
main routine are likely to be changed by the table read
instruction used in the ISR. Errors can occur. In other
words, using the table read instruction in the main rou-
tine and the ISR simultaneously should be avoided.
However, if the table read instruction has to be applied
in both the main routine and the ISR, the interrupt
should be disabled prior to the table read instruction.
@6
@6
*6
The instructions TABRDC [m] (the current page,
one page=256words), where the table locations is
defined by TBLP (07H) in the current page. And the
ROM code option TBHP is disabled (default).
The instructions TABRDC [m] , where the table lo-
cations is defined by registers TBLP (07H) and
TBHP (01FH). And the ROM code option TBHP is
enabled.
The instructions TABRDL [m] , where the table lo-
cations is defined by Registers TBLP (07H) in the
last page (1700H~17FFH).
TABRDL , transfer the contents of the
@5
@5
*5
@4
@4
*4
HT82K94E/HT82K94A
@3
@3
*3
@2
@2
*2
November 22, 2005
@1
@1
*1
@0
@0
*0