Z84C9008VSG Zilog, Z84C9008VSG Datasheet - Page 65

• Manufacturer Part Number: Z84C9008VSG
• Description: IC 8MHZ Z80 KIO 84-PLCC
• Manufacturer: Zilog
• Series: Z80r

Specifications of Z84C9008VSG

• Processor Type: Z80
• Features: Serial/Parallel Input/Output, Counter/Timer Circuit
• Speed: 8MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 84-LCC (J-Lead)
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Cpu Speed: 8MHz
• Digital Ic Case Style: LCC
• No. Of Pins: 84
• Supply Voltage Range: 5V
• Operating Temperature Range: 0°C To +70°C
• Svhc: No SVHC (18-Jun-2010)
• Rohs Compliant: Yes
• Base Number: 84
• Clock Frequency: 8MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

UM008005-0205
Modified Page Zero Addressing
The Z80 has a special single byte
locations in page zero of memory. This instruction, which is referred to as
a restart, sets the PC to an effective address in page zero. The value of this
instruction is that it allows a single byte to specify a complete 16-bit
address where commonly called subroutines are located, thus saving
memory space.
Relative Addressing
Relative addressing uses one byte of data following the Op Code to
specify a displacement from the existing program to which a program
jump can occur. This displacement is a signed two’s complement number
that is added to the address of the Op Code of the following instruction.
The value of relative addressing is that it allows jumps to nearby locations
while only requiring two bytes of memory space. For most programs,
relative jumps are by far the most prevalent type of jump due to the
proximity of related program segments. Thus, these instructions can
Significantly reduce memory space requirements. The signed
displacement can range between +127 and -128 from A+2. This allows
for a total displacement of +129 to -126 from the jump relative Op Code
address. Another major advantage is that it allows for relocatable code.
B7
Op Code
Op Code
Op Code
B0
Jump Relative (One Byte Op Code)
8-Bit Two’s Complement
Displacement Added to
Address (A+2)
One Byte
Effective Address is
(B5 B4 B3 000)2
CALL
instruction to any of eight
Z80 CPU Instruction Description
User’s Manual
Z80 CPU
45