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HMCS46C,HMCS~CL----------------------------------------------
______ _
Branch to Bank 0
•
LAI
16
·--LRA
7
~-.LPU
6
~
BR
3F
J
LAI
16
LBA
·--LRA
7
: COMB
L-_LPU
31
~
BR
3F
j
R,o • "1" (R'O • "0"1
BRL 6-3F
(Branch to Bank 0 5-3F (6-3FII
R,o ,. "1" (R'O • "0"1
BRL 31-3F
(Branch to Bank 0 31-3F (31-3FII
• CAL
By CAL instruction, subroutine jump to the Subroutine
Space is performed.
The Subroutine Space is the Bank 0 0 Page (0 Page).
The address next to CAL instruction address is pushed onto
the stack STl and the contents of the stacks STl, ST2 and ST3
are pushed onto the stacks ST2, ST3 and ST4 respectively as
shown in Figure 10.
Branch to Bank
1
The bank part of the program counter becomes the Bank 0
and the page part becomes the 0 Page. The lower 6 bits (operand
a, 06 to 01) of the ROM Object Code is transferred to the
address part of the program counter.
LAI
0
r--LRA
7
~-.LPU
16'
BR
3F
J
LAI
0
LTA
.--LRA
7
:
LVI
3
I
XMA
~-·LPU
10
~
BR
2E
j
R,o • "0" (R,o - "1"1
BRL 16-3F
(Branch to Bank 1 16-3F (47-3FII
R,o ,. "0" (R,o ,. "1"1
BRL 10-2E
(Branch to Bank 1 10-2E (42-2EII
Figure 8 BRL Example
The HMCS46C has 4 levels of stack (S1I, ST2, ST3 and ST4)
which allows the programmer to use up to 4 levels of subroutine
jumps (including interrupts).
CAL is a conditional instruction and executed only when the
Status F/F is "I". If the Status F/F is "0", it is skipped and the
Status F/F changes to "1".
• CALL
By CALL instruction, subroutine jump to an address in any
bank and page is performed.
Table 4 Bank Part Truth Table of TBR Instruction
Subroutine jump to any address can be implemented by the
subroutine jump to the page specified by LPU instruction in the
bank designated by the reversed-phase signal R?O of the Data
I/O Register R?O.
This instruction
is
a macro instruction of LPU and CAL
instructions, which is divided into two instructions as follows.
PC ..
P2
Bank Part of PC after
TBR
1 (Bank 11
1
1 (Bank 1)
0
1 (Bank 11
CALL
a-b_LPU a
CAL b
1
1 (Bank 11
o
(Bank 01
0
o
(Bank 01
<
SubroutineJump to Bank "R7o ", a Page - b Address>
•
SUBROUTINE JUMP
CALL instruction
is
conditional because of characteristics of
LPU and CAL instructions, and is executed when the Status F/F
is "1" If the Status F/F is "0", the instruction is skipped and
the Status F /F changes to "1". The examples of CALL instruc-
tion are shown in Figure 11.
There are two types of subroutine jumps. They are explained
in the following paragraphs.
/
(Page Pard
\
Ban~a;
r - -
Page Part
~;---
Address Part
~
(PCI
PC.. PC.. PC.
PC,
PC,
PC.
PC s
PC.
PC,
PC 2 PC.
PC.
'--'-T-
(Modification)
I P2
p.
p.
C
B,
B2
B.
B.
I
A, : A2 : A. : A.
I
L
_
~
_
~
_
~
__
~
__ L -__
L-~~~_L-~_~-L_~-L
___
~.
(PC after TBR
Instructionl
Figure 9 Modification of Program Counter by TBR Instruction
94
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