nsc800 National Semiconductor Corporation, nsc800 Datasheet - Page 27

• Manufacturer Part Number: nsc800
• Description: Nsc800tm High-performance Low-power Cmos Microprocessor
• Manufacturer: National Semiconductor Corporation

11 0 Addressing Modes
11 9 MODIFIED PAGE ZERO
A subset of NSC800 instructions (the Restart instructions)
provides a code-efficient single-byte instruction that allows
CALLs to be performed to any one of eight dedicated loca-
tions in page zero (locations X’0000 to X’00FF) Normally a
CALL is a 3-byte instruction employing direct memory ad-
dressing
Example
Instruction Perform a restart call to location X’0028
Mnemonic RST
Opcode
p
t
00H
000
08H
001
10H
010
X’28
18H
011
20H
100
(Continued)
28H
101
30H
110
TL C 5171– 55
38H
111
27
Program execution continues at location X’0028 after exe-
cution of a single-byte call employing modified page zero
addressing
11 10 BIT
The NSC800 allows setting resetting and testing of individ-
ual bits in registers and memory data bytes
Example
Operation Set bit 2 in the L register
Mnemonic SET
Opcode
Bit addressing allows the selection of bit 2 in the L register
selected by register addressing
2 L
TL C 5171 – 56