Xilinx CAST CZ80CPU User manual

January 2009
CZ80CPU
8-Bit Microprocessor
Core
The CZ80CPU implements a fast, fully-functional, single-chip, 8-bit microprocessor with
the same instruction set as the Z80.
The core has a 16-bit address bus capable of directly accessing 64kB of memory
space. It has 252 root instructions with the reserved 4 bytes as prefixes, and accesses
an additional 308 instructions.
The microcode-free design was developed for reuse in ASIC and FPGA implementa-
tions. It is strictly synchronous, with no internal tri-states and a synchronous reset.
Applications
The CZ80CPU is suitable for many embedded controller applications, including:
•industrial control systems
•point-of-sale terminals
•automotive controls
Block Diagram
Programming features contain
208 bits of read/write memory
that are accessible to the pro-
grammer.
The internal registers include an
accumulator and six 8-bit regis-
ters that can be paired as three
16-bit registers.
In addition to general registers,
a 16-bit stack-pointer, 16-bit
program-counter, and two 16-bit
index registers are provided.
Control Unit
o8-bit Instruction decoder
Arithmetic-Logic Unit
o8-bit arithmetic and logical
operations
o16-bit arithmetic operations
oBoolean manipulations
Register File Unit
oDuplicate set of both general
purpose and flag registers
oTwo 16-bit index registers
Interrupt Controller
oThree modes of maskable in-
terrupts
oNon maskable interrupt
External Memory interface
oCan address up to 64 KB of
program memory
oCan address up to 64 KB of
data memory
oCan address up to 64 KB of
input/output devices
On-core dynamic memory re-
fresh counter
Benefits
The core can be used as an
equivalent of the Zilog™ Z80,
which due to its popularity has a
variety of industry certified
software ready to be used
Easy implementation in SoC
designs targeted to FPGAs or
ASICs
Guarantees independence from
chip vendors

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Copyright © CAST, Inc. 2009, All Rights Reserved.
Contents subject to change without notice.
Trademarks are the property of their respective owners.
Functional Description
The CZ80CPU core is partitioned into modules as shown in
the Block Diagram and described below.
Cycle Control
The main control machine, which synchronizes all the others.
It has an instruction register and all registers controlled inter-
rupts, bus request cycle, wait states etc. This unit controls
bus control signals too.
Bus Control
Registers are triggered on the falling edge and or gates.
These are used to form the bus control timing, changed on
both clock edges. This is the only unit that has registers syn-
chronized on the falling clock edge.
Address Unit
This unit controls all operations on addresses (calculates the
next instruction address, nested data address, jump and re-
turn address etc.) and increments and decrements the 16-bit
addr register. It includes pc_reg (program counter), sp_reg
(stack pointer), i_reg (interrupt register) and r_reg (refresh
register).
NMI Control
This unit detects a falling edge on the nmin pin. If detected,
the internal nmi register is set and this causes a non-
maskable interrupt service cycle.
Reset Control
This unit controls the state of external signal resetn. If it has
value ‘0’ for at least three full clock cycles, then it sets the in-
ternal synchronous reset signal (rst) to ‘1.’
Register Bank
This includes all the commonly used registers (based and al-
ternative) and the logic element needed to change the data in
these registers.
Arithmetic-Logic Unit (ALU)
The unit accumulator and flag registers, and performs 8-bit
arithmetic and logic operations, 16-bit arithmetic operations
(without increment and decrement), bit operations, and sets
the flag register.
Implementation Results
The CZ80CPU is a technology independent design that can
be implemented in a variety of process technologies. The
following are typical Xilinx results with Fmax optimized for
speed.
Family Fmax
(MHz)Slices IOB GCLK BRAM MULT DCM/
DLL MGT PPC Design
Tools
Virte
x
-II Pro
XC2VP4-7 78 2102 38 1 0 0 0 0 0 ISE 5.2i
Virte
x
-E
XCV400E-8 45 2060 38 1 0 N/A 0 N/A N/A ISE 5.2i
Virte
x
-II
XC2V500-6 76 2003 38 1 0 0 0 N/A N/A ISE 5.2i
Spartan-IIE
XC2S300E-7 38 2388 38 1 0 N/A 0 N/A N/A ISE 5.2i
Spartan-3
XC3S400-4 36 1967 38 1 0 0 0 N/A N/A ISE 5.2i
Support
The core as delivered is warranted against defects for three
years from purchase. Thirty days of phone and email tech-
nical support are included, starting with the first interaction.
Additional maintenance and support options are available.
Verification
The CZ80CPU core’s functionality was verified by means of a
proprietary hardware modeler. The same stimulus was ap-
plied to a hardware model that contained the original Zilog
Z84C00 chip, and the results compared with the core’s simu-
lation outputs.
Deliverables
The core is available in ASIC (synthesizable HDL) and FPGA
(netlist) forms, and includes everything required for success-
ful implementation. The Xilinx version includes:
•Post-synthesis EDIF netlist
•Example CZ80CHIP – 8051 compatible design. This de-
sign uses the CZ80CPU and illustrates how to build and
connect memories and port modules
•Sophisticated HDL Testbench that instantiates the exam-
ple design CZ80CHIP, external RAM, external ROM, clock
generator, and process that compares your simulation re-
sults with the expected results
•A collection of Z80 assembler programs which are ex-
ecuted directly by the Test Bench
•Simulation script, vectors, expected results, and compari-
son utility
•Place and route script
•Comprehensive user documentation, including architec-
tural overview, hardware description, user guide, detailed
specifications and a system integration guide