ht82k74e Holtek Semiconductor Inc., ht82k74e Datasheet - Page 9

• Manufacturer Part Number: ht82k74e
• Description: 27mhz Keyboard/ Mouse Tx 8-bit Mcu
• Manufacturer: Holtek Semiconductor Inc.

Program Memory
The Program Memory is the location where the user
code or program is stored. The device is supplied with
One-Time Programmable, OTP, memory where users
can program their application code into the device. By
using the appropriate programming tools, OTP devices
offer users the flexibility to freely develop their applica-
tions which may be useful during debug or for products
requiring frequent upgrades or program changes. OTP
devices are also applicable for use in applications that
require low or medium volume production runs.
Structure
The Program Memory has a capacity of 2K 15 bits. The
Program Memory is addressed by the Program Counter
and also contains data, table information and interrupt
entries. Table data, which can be setup in any location
within the Program Memory, is addressed by separate
table pointer registers.
Special Vectors
Within the Program Memory, certain locations are re-
served for special usage such as reset and interrupts.
Rev. 1.00
Logic operations: AND, OR, XOR, ANDM, ORM,
XORM, CPL, CPLA
Rotation RRA, RR, RRCA, RRC, RLA, RL, RLCA,
RLC
Increment and Decrement INCA, INC, DECA, DEC
Branch decision, JMP, SZ, SZA, SNZ, SIZ, SDZ,
SIZA, SDZA, CALL, RET, RETI
Location 000H
This vector is reserved for use by the device reset for
program initialisation. After a device reset is initiated,
the program will jump to this location and begin execu-
tion.
Program Memory Structure
9
Location 008H
This 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 timer interrupt is
enabled and the stack is not full.
Table location
Any location in the program memory can be used as
look-up tables. There are three methods 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).
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 TBHP function selected via a
configuration option 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 instruc-
tion, 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. It
will not be enabled until the TBLH has been backed
up. All table related instructions require two cycles to
complete the operation. These areas may function as
normal program memory depending on the require-
ments.
Once TBHP is enabled, the instruction TABRDC [m]
reads the ROM data as defined by TBLP and TBHP
value. Otherwise, the TBHP function selected via a
configuration option is disabled, the instruction
TBLP and the current program counter bits.
TABRDC [m] reads the ROM data as defined by
The three methods are shown as follows: The in-
structions TABRDC [m] (the current page, one
page=256words), where the table locations is de-
fined by TBLP (07H) in the current page. And the
TBHP function selected via a configuration option is
disabled (default).
The instruction TABRDC [m] , where the table lo-
cation is defined by registers TBLP (07H) and
TBHP (01FH). And the TBHP function selected via
a configuration option is enabled.
The instructions TABRDL [m] , where the table lo-
cations is defined by Registers TBLP (07H) in the
last page (700H~7FFH).
TABRDL , transfer the contents of the
HT82K74E/HT82K74EE
December 15, 2009