dp8344b National Semiconductor Corporation, dp8344b Datasheet - Page 139

• Manufacturer Part Number: dp8344b
• Description: Biphase Communications Processor?bcp
• Manufacturer: National Semiconductor Corporation

Figure 6-2
6 0 Reference Section
CALL Unconditional Relative Call
Syntax
CALL n
Affected Flags
None
Description
Pushes the Program Counter the ALU flags the Global In-
terrupt Enable bit GIE and the current register bank selec-
tions onto the internal Address Stack then unconditionally
transfers control to the instruction at the memory address
calculated by adding the contents of the Program Counter
to the immediate value n (sign extended to 16 bits) Since
the immediate value n is an 8-bit two’s complement dis-
placement the unconditional relative call’s range is from
the Program Counter initially contains the memory address
of the next instruction following the call
Example
Transfer control to the subroutine ‘‘Send it’’ Note that
‘‘Send it’’ must be within
PC
Instruction Format
T-states
3
Bus Timing
Operation
PC
PC
a
1
15
127 to
CALL
x
a
1
Address Stack
GIE
n(sign extended)
0
b
Opcode
128 relative to the Program Counter Note that
Send it
0
ALU flags
1
1
x
0
immediate
a
register bank selections
127
0
PC
7
b
128 words relative to the
(Continued)
n
0
139
Figure 6-1
CMP Compare
Syntax
CMP rs n
Affected Flags
N Z C V
Description
Compares the immediate value n with the source register rs
by subtracting n from rs The affected flags are updated but
the result is not saved Note that only the active registers
R0 – R15 may be specified for rs The value of n is limited to
8 bits (unsigned range 0 to 255 signed range
Example
Compare the data byte in register 11 to the ASCII character
‘‘A’’
Compare the contents of register 8 to the value 25
Note
Instruction Format
T-states
2
Bus Timing
Operation
rs
b
0
15
128)
CMP
JC
JEQ
CMP
BIT
JZ
b
Opcode
0
l
n
e
e
Comparison
LT
LEQ
EQ
GEQ (
GT
logical OR
1
logical AND
R11 ‘‘A’’
Less than A
Equal to A
R8 25
CCR 00000011B
Greater than
1
Comparing of Unsigned Values
(
(
(
(
k
k
l
l
e
11
)
e
e
)
)
)
)
limited register immediate
n
If
else data
if
Flag(s) to Test
data
data
data
Goto Greater than
C
C
C
C
Z
k
e
l
l
l
Z
‘‘A’’
Z
‘‘A’’
‘‘A’’
3
25
a
rs
127 to
0