CZ80PIO
Peripheral Device
Megafunction
General Description
The CZ80PIO, hereinafter referred to as PIO, is a dual-port device which can be programmed by the system
software to function as a broad range of peripheral devices that are compatible with the Z80CPU such as most
keyboards, printers etc.
System design is simplified because the PIO connects directly to the Z80CPU with no additional logic. In larger
systems, address decoders and buffers may be required.
The CZ80PIO is a microcode-free design developed for reuse in ASIC and FPGA implementations. The design
is strictly synchronous, with no internal tri-states and a synchronous reset.
Symbol
8
8
data_i
data_o
data_tri
Features
ardy
astb_n
porta_i
porta_o
porta_tr
8
8
8
•
•
•
Provides a direct interface between Z80
microprocessor systems and peripheral
devices
Two ports with interrupt-driven handshake for
fast response
Four programmable operating modes:
•
Output Mode (both ports)
•
Input Mode (both ports)
•
Bi-directional (Port A only)
•
Bit Control Mode (both ports)
Programmable interrupts on peripheral status
conditions
clk
cdselect
portselect
ce_n
CZ80PIO
m1_n
iorq_n
rd_n
int_n
ieo
iei
brdy
bstb_n
portb_i
portb_
o
8
8
8
•
Applications
•
•
Programmable, dual - port device
Interface for a wide range of peripheral
devices such as:
•
Keyboards
•
•
•
Printers
Paper table readers
PROM programmers etc.
CAST, Inc.
May 2004
Page 1
CZ80PIO Megafunction Datasheet
Pin Description
Name
Type Description
Clock
clk
In System Clock
Interface to Processor
Out Tristate controller for buffer for data
bus
data_i
In Data bus input
data_o
Out Data bus output:
rd_n
In Read Cycle Status
iorq_n
In Input / Output Request
ce_n
In Chip Enable
cdselect
In Control / Data select
portselect In Port B / A select
m1_n
In Machine Cycle One
Interrupt Service Routine
int_n
In Interrupt Request
iei
In Interrupt Enable Input
ieo
Out Interrupt Enable Output
Control
porta_tri In Tristate controller for buffer for data
bus
porta_i
In Port B bus input
porta_o Out Port B bus output
portb_tri In Tristate controller for buffer for data
bus
portb_i
In Port B bus input
portb_o Out Port B bus output
ardy
Out Register A ready
brdy
Out Register B ready
astb_n
In Port A strobe pulse from peripheral
device
bstb_n
In Port B strobe pulse from peripheral
device
data_tri
register specifies which of the eight data bits in
the port are to be outputs and enables these
bits; the remaining bits are inputs. The mask
register specifies which of the bits in the port
are masked.
Control logic
The control logic consists of the CPU bus
interface logic, interrupt control logic and internal
control logic. The CPU bus interface logic
interfaces the CZ80PIO directly to the CZ80CPU,
so no external logic is necessary. For large
systems, however, address decoders and/or
buffers may be necessary. The interrupt control
logic section handles all CPU interrupt protocol
for nested-priority interrupt structures. Any
device's physical location in a daisy-chain
configuration determines its priority. Two lines
(IEO and IEI) are provided in each PIO to form
this daisy chain. The device closest to the CPU
has the highest priority. Within a PIO, port A
interrupts have higher priority then those of port
B. In the byte input, byte output or bi-directional
modes, an interrupt can be generated whenever
the peripheral requests a new byte transfer. In
the bit control mode, an interrupt can be
generated when the peripheral status matches a
programmed value.
Functional Description
The CZ80PIO megafunction is partitioned into
modules as shown in figure 1 and described
below.
Port Logic
Each port contains separate input and output
registers, handshake control logic and the
control registers. All data transfers between the
peripheral unit and the CPU use the data input
and output registers. The handshake logic
associated with each port controls the data
transfers through the input and the output
registers. The mode control register (two bits)
selects one of the four programmable operating
modes. The Bit Control mode (mode 3) uses the
remaining registers. The input/output control
CAST, Inc.
Page 2
CZ80PIO Megafunction Datasheet
Deliverables
Netlist License
HDL Source License
•
•
•
•
•
•
•
Post-synthesis EDIF netlist
Testbench (self checking)
Vectors for testing the functionality of the
megafunction
Place & Route Script
Constraint file
Simulation script
Documentation
•
•
•
•
•
•
VHDL or Verilog RTL source code
Testbench (self checking)
Vectors for testing the functionality of the
megafunction
Simulation scripts
Synthesis scripts
Documentation
Verification Methods
The CZ80PIO megafunction’s functionality was verified by means of a proprietary hardware modeler. The
same stimulus was applied to a hardware model that contained the original Zilog Z80PIO chip, and the results
compared with the megafunction’s simulation outputs.
Megafunction Modifications
The CZ80PIO megafunction can be modified to include additional new ports. Please contact CAST, Inc. directly
for any required modifications.
Contact Information
CAST, Inc.
11 Stonewall Court
Woodcliff Lake, New Jersey 07677 USA
Phone: +1 201-391-8300
Fax:
+1 201-391-8694
E-Mail:
info@cast-inc.com
URL:
www.cast-inc.com
This megafunction developed by peripheral
controller experts at Evatronix SA
Copyright © CAST, Inc. 2004, All Rights Reserved. Contents subject to change without notice
CAST, Inc.
Page 4
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