Table of Contents
Advertisement
LCO-IV------------------------------------------------------------------
Pattern of AOM
Loaded into the accumulator
and B register
Figure 5 Correspondence of Each Bit of Pattern
Table 3 Example of Pattern Instructions
Before Execution
Referred ROM
ROM
After Execution
PC
p
C
B
A
Address
Pattern
B
A
R2
R3
Bank 00-3F
1
0
A
0
Bank 0 10-20
120
2
B
.
(0-3F)
(10-20)
-
-
Bank 00-3F
7
1
4
0
Bank 1 29-00
220
4
B
(0-3F)
(61-00)
-
-
Bank 1 30-00
4
0/1··
0
9
Bank 1 30-09
320
2
B
4
B
(62-00)
(62-09)
Bank 1 30-00
1
0/1**
F
9
Bank 131-39
223
4
C
(62-00)
(63-39)
-
-
• "-" means that the value does not change after execution of the instruction.
"0/1" means that either "0" or "1" may
be
selected.
• BRANCH
ROM is accessed according to the program counter sequence
and the program is executed. In order to jump to any address
out of the sequence, there are four ways_ They are explained in
the following paragraphs_
• BR
By BR instruction, the program branches to an address in the
current page.
The lower 6 bits of ROM Object Code (operand a, 0
6
to 0
1 )
are transferred to the address part of the program counter. This
instruction is a conditional instruction and executed only when
the Status F
IF
is "1". If it is "0", the instruction is skipped and
the Status F
IF
becomes" 1". The operation is shown in Figure 6.
• LPU
By LPU instruction, the jump of the bank and page is per-
formed.
The lower 5 bits of the ROM Object Code (operand u,Os
to
0.)
are transferred to the page part of the program counter
with a delay of 1 instruction cycle time. At the same time, the
signal R?O (the reversed-phase signal of the Data
1/0
Register
R?O) is transferred to the bank part of the program counter with
a delay of 1 instruction cycle time. The operation is shown in
Figure 7_
Consequently, the bank and page will remain unchanged in
the cycle immediately following this instruction. In the next
cycle, a jump of the bank and page is achieved.
This instruction (LPU) is conditional, and is executed only
when the Status
F/F
is "I". Even after a skip, the Status
F/F
190
will remain unchanged ("0").
LPU instruction is used in combination with BR instruction
or CAL instruction as the macro instruction of BRL or CALL
instruction.
• BRL
By BRL instruction, the program branches to an address in
any bank and page.
This insiruction is a macro instruction of LPU and BR
instructions, which is divided into two instructions as follows.
BAL
a - b - LPU
a
BA
b
<Jump to Bank "R,o",a Page -
b
Address
>
BRL instruction is a conditional instruction because of
characteristics of LPU and BR instructions, and is executed only
when the Status F
IF
is "I ". I f the Status F
IF
is "0", the instruc-
tion is skipped and the Status F
IF
becomes "1". The examples
of BRL instruction are shown in Figure 8.
• TBR (Table Branch)
By TBR instruction, the program branches by the table.
The program counter is modified with the accumulator, the
B register, the Carry
F/F
and the operand p-
The method for modification is shown in Figure 9.
The bank part is determined by the logical equation:
PClI +
P2,
as shown in Table 4.
If the address where TBR instruction exists is in the Bank 1,
Advertisement
Table of Contents
