ZiLOG Z80 User Manual

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Address Selection
Themodule’s address canbe set to anyaddress thatis a multiple of 4, suchas
address 0, 4,8, 12, 16, … , 252. This address is known asthe base address, withthe
moduleoccupying thisaddress plus the nextthreeaddresses. Thus if the base
address is 0, then the module occupies the address range 0 to 3.
Theaddress is set with the 6 wayDIP switchSW1.
Thesix address switches, 1 to 6, represent addresses 128, 64, 32, 16, 8 and 4
respectively.Thebase address isthe sumof allthe switches in theOffposition.For a
pianostyle DIPswitch, as illustratedbelow, Upis Off andDownis On.
Inthe illustration below theswitches are:
Up Down Down Down Up Down
Thisrepresentsthe address:
128 + 0 + 0 + 0 + 8 + 0
= 128 + 8
= 136 (or 0x88in hexadecimal).
Inorder to provide somecertaintyfor software itis strongly recommendedyou set
the base addressof your first PIOmoduleto 0x68. Ifyou havea secondPIO module
the recommendedbase address is 0x6C. Ifeverybodyfollowsthis recommendation
thensoftware writtenforthe PIOmodulewill knowwhereto find thehardware.

ZiLOG Z80 Specifications

General

Manufacturer	ZiLOG
Introduction Year	1976
Clock Speed	2.5 MHz to 20 MHz
Data Width	8-bit
Address Width	16-bit
Instruction Set	Z80
Transistor Count	8, 500
Package	40-pin DIP
Category	Microprocessor
Memory Address Space	64 KB
Voltage Supply	5V