Actel MC-ACT-6809 Software compatible 6809 cpu Datasheet

MC-ACT-6809
Software Compatible 6809 CPU
February 25, 2003
Datasheet v1.2
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TM
Product Summary
Intended Use
•
Replacing existing 6809 designs
•
System integration of 6809 designs
•
Designs with complex 8bit processors
Key Features
•
6809 Software Compatible
•
Illegal Opcode Recognition
•
On-chip Bus Concept
•
Fully Synchronous
Targeted Devices
•
Axcelerator Family
•
ProASIC
•
SX-A/SX, RTSX Family
PLUS
Family
General Description
The MC-ACT-6809 is a software compatible 6809 microprocessor implemented in VHDL using a structured and
synchronous design methodology. This flexible 8-bit microprocessor can be used for low to mid range applications
and is easily integrated into recent Actel FPGA technologies. The 6809 is designed that application specific
performance enhancements (e.g., high-speed multiplier) can be integrated, too.
Memec Design built a simulation and a hardware verification environment. The simulation environment is VHDL
based and simulates the synthesizable VHDL code of the 6809. This functional VHDL testbench reading instruction
code from a file can be used for performance check, software verification or to get used to the functionality.
A demonstration board is available which shows the functionality of the 6809 in a hardware testbench.
February 25, 2003
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Software Compatible 6809 CPU
Memec Design
Core Deliverables
•
Netlist Version
o Netlist compatible with the Actel Designer place and route tool
•
RTL Version
o VHDL Source Code
o Test Bench
•
All
o
User Guide
Synthesis and Simulation Support
•
Synthesis: Synplicity
•
Simulation: ModelSim
•
Other tools supported upon request
Verification
clk
reset_n
irq_n
firq_n
nmi_n
6809
Status Information
Test Bench
Interrupts
•
seq_state
cc
pc
stack
stack_operation
opcode
bus_addr
bus_rd_data
Bus Interface Unit
bus_wr_data
bus_rw_n
rd_trf_ebl
wr_trf_ebl
bus_busy
Bus Request Unit
bus_want
mem_rdy
Figure 1: Logic Symbol
February 25, 2003
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Software Compatible 6809 CPU
Memec Design
Functional Description
Structure of 6809
The block diagram below shows the index arithmetic unit, the data ALU, command sequencer, memory fetch unit
and program counter.
S
U
Command
Sequencer
X
Index ALU
Y
D=A:B
Memory
Fetch Unit
B
A
DP
Data ALU
CC
PC
Address Register
Write Data Register
Read Data Register
Figure 2: Block Diagram
The memory interface contains registered read and write data and address registers, which makes the design of the
interface easier for timing verification etc.
Internal Registers
The following part describes the existing registers in the MC-ACT-6809:
Index Registers (X,Y)
The index registers are used in indexed mode of addressing and are used for calculating the effective addresses.
During some indexed modes, the contents of the index register are incremented or decremented to point to the next
item of tabular type data. All 4 pointer register (U, S, X, Y) can be used as index register.
Stack Pointer Registers (U,S)
The system stack pointer S is automatically used by the processor during subroutine calls and interrupts! The user
stack pointer is controlled by the programmer. Both stack pointers point to the top of the stack.
Program Counter Register
The program counter (PC) points to the address of the next instruction to be executed.
Accumulators (A,B,D)
The A and B accumulators are general purpose registers. Some instructions concatenate the registers A and B to
achieve 16 bit values. This register is then referred as the D register with the A register as most significant byte.
February 25, 2003
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Software Compatible 6809 CPU
Memec Design
Condition Code (CC) Register
Beginning with bit(0) the condition code register contains following flags:
C:
Carry from ALU
V:
Overflow (2 complement) from ALU
Z:
Zero from ALU
N:
Negative (2 complement) from ALU
I:
Interrupt mask register for irq_n
H:
Half Carry (low nibble) from ALU
F:
Interrupt mask for firq_n
E:
Entire Flag for irq_n/firq_n stack operations
Direct Page (DP) Register
These registers enhance the direct addressing mode. During direct addressing instruction execution, the contents of
DP appears at the higher address outputs (A15- A8).
Instructions
The MC-ACT-6809 supports all 6809 instructions like load, store, and, or, add, sub, transfer/exchange instructions
for all registers, 8 by 8 unsigned multiply, decimal adjust and signed/unsigned conditional branches. A powerful
stack command is also available. Software interrupts are supported.
Addressing Modes
Nearly all instructions can be combined with the following addressing modes:
Inherent:
Register source and destination, no post bytes, e.g. INCA
Immediate:
Postbyte is parameter, e.g. LDA #100
Extended:
Postbytes are address, e.g. LDA 1000
Direct:
Postbyte is low address, DP is high address, e.g. LDA <50
Indexed:
Postbyte(s) define indexed mode:
- (Index registers are X,Y,U,S)
- Post incr. by 1 and 2, e.g. LDA ,S++
- Pre decr. by 1 and 2, e.g. LDA ,-X
- Zero offset, e.g. LDA 0,X
- signed offset, e.g. LDA -7,Y
- A/B/D signed offset, e.g. LDB A,U
- 8/16bit signed offset PC relative, e.g. LDA 665,PCR
Indexed indirect: The same types as indexed may be used. The indirect mode uses the argument of the index mode
as address for an indirect access.
Illegal Instructions
To insure save operation, illegal opcodes are recognized and will lead to an exception, where a vector is fetched to
enter the exception handler routine. For this purpose, the reserved vector of the 6809 is used. The address of the
illegal instruction is pushed on the S stack.
February 25, 2003
Optimized for
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Software Compatible 6809 CPU
Memec Design
Interrupts
For interrupting the MC-ACT-6809, there are 3 level-sensitive interrupts:
irq_n:
standard interrupt or interrupt request, low_active, pushes all registers on stack:
PC(Low), PC(High), U(Low), U(High), Y(Low), Y(High), X(Low), X(High), DP, B, A, CC
firq_n: fast interrupt, pushes only PC and CC on stack: PC(Low), PC(High), CC
nmi_n: non maskable interrupt, pushes all registers on stack:
PC(Low), PC(High), U(Low), U(High), Y(Low), Y(High), X(Low), X(High), DP, B, A, CC
The nmi_n is masked after reset until the system stack pointer is initialized.
The different interrupts will fetch the corresponding vector for the interrupt in the memory:
0xfff0 Illegal Instruction
0xfff2 SWI3
0xfff4 SWI2
0xfff6 FIRQ
0xfff8 IRQ
0xfffa SWI
0xfffc NMI
0xfffe RESET
The interrupt behavior of the MC-ACT-6809 matches exactly the one of the original 6809 in terms of results in
registers and memory. An exception is the case where an illegal instruction is decoded by the 6809: in this case, the
reserved interrupt is used.
February 25, 2003
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Software Compatible 6809 CPU
Memec Design
Device Requirements
Family
SX-A
PLUS
ProASIC
Axcelerator
Device
COMB
1625 (91%)
n/a
1577 (30%)
SX32A-3
APA150-STD
AX500-3
Utilization
SEQ
344 (32%)
n/a
339 (13%)
Performance
Total
1969 (69%)
2795 (46%)
1916 (24%)
28 MHz
11 MHz
31 MHz
Table 1: Device Utilization and Performance
Verification and Compliance
Functional and timing simulation has been performed on the 6809 using VHDL and Verilog Test Benches.
Simulation vectors used for verification are provided with the core. This core has also been used successfully in
customer designs.
Signal Descriptions
The following signal descriptions define the IO signals.
Signal
Direction Description
clk
in
system clock, rising edge used only
reset_n
in
asynchronous system reset, active low, goes to all flip flops
nmi_n
in
Non maskable interrupt, active low
firq_n
in
Fast interrupt request, active low
irq_n
in
Interrupt request, active low
bus_busy
in
Bus busy, If ‘1’ the uP can not access the bus and waits until bus is released.
wr_trf_ebl
out
Write transfer enable
bus_want
out
Bus want. The uP requests the bus.
rd_trf_ebl
out
Read transfer enable
rw_n
out
Read / write-not. If ‘1’ then read cycle
bus_addr[15:0]
out
Bus address
bus_rd_data[7:0]
in
Read data
bus_wr_data[7:0]
out
Write data
mem_rdy
out
Memory ready, see ‘Internal Bus Interface Timing’ for timing diagram
seq_state[5:0]
out
Command sequencer state register
cc[7:0]
out
Condition code register
pc[15:0]
out
Program counter register
stack[15:0]
out
Stack pointer
stack_operation
out
Stack operation, if ‘1’ a stack operation cycle is running
opcode[5:0]
out
Operation code
Table 2: Core I/O Signals
February 25, 2003
Optimized for
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Software Compatible 6809 CPU
Memec Design
Recommended Design Experience
For the source version, users should be familiar with HDL entry and Actel design flows. Users should be familiar
with Actel Libero v2.2 Integrated Design Environment (IDE) and preferably with Synplify and ModelSim.
Ordering Information
Part Number
MC-ACT-6809-NET
MC-ACT-6809-VHD
Description
Core Netlist
Core VHDL
Table 3: Core Part Numbers
The CORE is provided under license from Memec Design for use in Actel programmable logic devices. Please
contact Memec Design for pricing and more information.
Information furnished by Memec Design is believed to be accurate and reliable. Memec Design reserves the right to
change specifications detailed in this data sheet at any time without notice, in order to improve reliability, function or
design, and assumes no responsibility for any errors within this document. Memec Design does not make any
commitment to update this information.
Memec Design assumes no obligation to correct any errors contained herein or to advise any user of this text of any
correction, if such be made, nor does the Company assume responsibility for the functioning of undescribed
features or parameters. Memec Design will not assume any liability for the accuracy or correctness of any support
or assistance provided to a user.
Memec Design does not represent that products described herein are free from patent infringement or from any
other third-party right. No license is granted by implication or otherwise under any patent or patent rights of Memec
Design.
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Datasheet Revision History
Version
Datasheet 1.0
Datasheet 1.1
Datasheet 1.2
February 25, 2003
Date
December 19, 2002
January 23, 2003
February 25, 2003
Description
First Release
Modification done in section core deliverables, Added logo to footer
Modification done in section device requirements, new URL and address
inserted
Optimized for
7
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