HT82K68 Holtek Semiconductor Inc, HT82K68 Datasheet - Page 8

• Manufacturer Part Number: HT82K68
• Description: Multimedia Keyboard Encoder OTP
• Manufacturer: Holtek Semiconductor Inc

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Note: *11~*0: Program counter bits
Initial reset
Timer counter overflow
Skip
Loading PCL
Jump, call branch
Return from subroutine
Location 008H
This area is reserved for the timer counter in-
terrupt service program. If timer interrupt re-
sults from a timer counter overflow, and if the
interrupt is enabled and the stack is not full,
the program begins execution at location
008H.
Table location
Any location in the PROM space can be used
as look-up tables. The instructions TABRDC
[m] (the current page, 1 page=256 words) and
TABRDL [m] (the last page) transfer the con-
tents of the 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 table is well-defined,
the other bits of the table word are trans-
ferred to the lower portion of TBLH, the re-
maining 1 bit is read as 0. The Table
Higher-order byte register (TBLH) is read
only. The TBLH is read only and cannot be re-
stored. If the main routine and the ISR (Inter-
rupt 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. Er-
rors can occur. In other words, using the table
read instruction in the main routine and the
ISR simultaneously should be avoided. How-
#11~#0: Instruction code bits
Mode
#11 #10
S11 S10 S9
*11 *10
*11 *10
0
0
Preliminary
0
0
*9
*9
#9
0
0
8
S8
*8
*8
#8
S11~S0: Stack register bits
@7~@0: PCL bits
0
0
ever, if the table read instruction has to be ap-
plied in both the main routine and the ISR,
the interrupt is supposed to be disabled prior
to the table read instruction. It will not be en-
abled until the TBLH has been backed up.
The table pointer (TBLP) is a read/write regis-
ter (07H), which indicates the table location.
Before accessing the table, the location must be
placed in TBLP. All table related instructions
need 2 cycles to complete the operation. These
areas may function as normal program memory
depending upon the requirements.
Program Counter
@7
S7
*7
#7
0
0
@6
S6
*6
#6
0
0
PC+2
Program memory
@5
#5
S5
*5
0
0
@4
S4
*4
#4
0
0
@3
*3
#3
S3
0
1
@2
*2
#2
S2
HT82K68E
0
0
August 8, 2000
@1
S1
*1
#1
0
0
@0
S0
*0
#0
0
0