ADUC7023 Analog Devices, ADUC7023 Datasheet - Page 19

• Manufacturer Part Number: ADUC7023
• Description: Precision Analog Microcontroller, 12-Bit Analog I/O, ARM7TDMI MCU
• Manufacturer: Analog Devices

Specifications of ADUC7023

• Mcu Core: ARM7 TDMI
• Mcu Speed (mips): 40
• Sram (bytes): 8192Bytes
• Gpio Pins: 20
• Adc # Channels: 12
• Other: PWM

OVERVIEW OF THE ARM7TDMI CORE
The ARM7® core is a 32-bit reduced instruction set computer
(RISC). It uses a single 32-bit bus for instruction and data. The
length of the data can be 8 bits, 16 bits, or 32 bits. The length of
the instruction word is 32 bits.
The ARM7TDMI is an ARM7 core with four additional features: T
support for the thumb (16-bit) instruction set, D support for
debug, M support for long multiplications, and I includes the
EmbeddedICE module to support embedded system debugging
THUMB MODE (T)
An ARM instruction is 32 bits long. The ARM7TDMI
processor supports a second instruction set that has been
compressed into 16 bits, called the Thumb® instruction set.
Faster execution from 16-bit memory and greater code density
can usually be achieved by using the Thumb instruction set
instead of the ARM instruction set, which makes the
ARM7TDMI core particularly suitable for embedded
applications.
However, the Thumb mode has two limitations. Thumb code
typically requires more instructions for the same job. As a
result, ARM code is usually best for maximizing the
performance of time critical code. Also, the Thumb instruction
set does not include some of the instructions needed for
exception handling, which automatically switches the core to
ARM code for exception handling.
See the ARM7TDMI user guide for details on the core
architecture, the programming model, and both the ARM
and ARM Thumb instruction sets.
LONG MULTIPLY (M)
The ARM7TDMI instruction set includes four extra instruc-
tions that perform 32-bit by 32-bit multiplication with a 64-bit
result, and 32-bit by 32-bit multiplication-accumulation (MAC)
with a 64-bit result. These results are achieved in fewer cycles
than required on a standard ARM7 core.
EmbeddedICE (I)
EmbeddedICE provides integrated on-chip support for the core.
The EmbeddedICE module contains the breakpoint and watch-
point registers that allow code to be halted for debugging purposes.
These registers are controlled through the JTAG test port.
When a breakpoint or watchpoint is encountered, the processor
halts and enters debug state. Once in a debug state, the
processor registers can be inspected as well as the Flash/EE,
SRAM, and memory mapped registers.
Rev. B | Page 19 of 96
EXCEPTIONS
ARM supports five types of exceptions and a privileged
processing mode for each type. The five types of exceptions are:
•
•
•
•
•
Typically, the programmer defines interrupt as IRQ, but for
higher priority interrupt, that is, faster response time, the
programmer can define interrupt as FIQ.
ARM REGISTERS
ARM7TDMI has a total of 37 registers: 31 general-purpose
registers and six status registers. Each operating mode has
dedicated banked registers.
When writing user-level programs, 15 general-purpose 32-bit
registers (R0 to R14), the program counter (R15), and the
current program status register (CPSR) are usable. The
remaining registers are only used for system-level programming
and exception handling.
When an exception occurs, some of the standard registers are
replaced with registers specific to the exception mode. All excep-
tion modes have replacement banked registers for the stack
pointer (R13) and the link register (R14) as represented in
Figure 14. The fast interrupt mode has more registers (R8 to R12)
for fast interrupt processing. This means the interrupt processing
can begin without the need to save or restore these registers,
and thus save critical time in the interrupt handling process.
USER MODE
Normal interrupt or IRQ. This is provided to service
general-purpose interrupt handling of internal and
external events.
Fast interrupt or FIQ. This is provided to service data
transfers or communication channels with low latency. FIQ
has priority over IRQ.
Memory abort.
Attempted execution of an undefined instruction.
Software interrupt instruction (SWI). This can be used to
make a call to an operating system.
R15 (PC)
CPSR
R10
R11
R12
R13
R14
R0
R1
R2
R3
R4
R5
R6
R7
R8
R9
SPSR_FIQ
R10_FIQ
R11_FIQ
R12_FIQ
R13_FIQ
R14_FIQ
R8_FIQ
R9_FIQ
Figure 14. Register Organization
MODE
FIQ
SPSR_SVC
R13_SVC
R14_SVC
MODE
SVC
SPSR_ABT
R13_ABT
R14_ABT
ABORT
MODE
USABLE IN USER MODE
SYSTEM MODES ONLY
SPSR_IRQ
R13_IRQ
R14_IRQ
MODE
IRQ
ADuC7023
UNDEFINED
SPSR_UND
R13_UND
R14_UND
MODE