DS4830_1110 Datasheet, PDF (17/29 Pages) Maxim Integrated Products – Optical Microcontroller

DS4830
Optical Microcontroller
Detailed Description
The following is an introduction to the primary features of
the DS4830 system management microcontroller. More
detailed descriptions of the device features can be found
in the DS4830 User’s Guide.
MAXQ20 Core Architecture
Instruction Set
The instruction set is composed of fixed-length, 16-bit
instructions that operate on registers and memory loca-
tions. The instruction set is highly orthogonal, allowing
arithmetic and logical operations to use any register
along with the accumulator. Special-function registers
control the peripherals and are subdivided into register
modules.
The device employs a MAXQ20 low-power, low-cost,
high-performance, CMOS, fully static, 16-bit RISC micro-
controller with flash memory. It is structured on a highly
advanced, 16 accumulator-based, 16-bit RISC archi-
tecture. Fetch and execution operations are completed
in one cycle without pipelining, since the instruction
contains both the op code and data. The highly efficient
core is supported by 16 accumulators and a 16-level
hardware stack, enabling fast subroutine calling and task
switching. Data can be quickly and efficiently manipulat-
ed with three internal data pointers. Multiple data point-
ers allow more than one function to access data memory
without having to save and restore data pointers each
time. The data pointers can automatically increment or
decrement following an operation, eliminating the need
for software intervention.
Module Information
The MAXQ20 architecture is designed to be modular and
expandable. Top-level instruction decoding is extremely
simple and based on transfers to and from registers. The
registers are organized into functional modules, which
are in turn divided into the system register and peripheral
register groups.
Peripherals and other features are accessed through
peripheral registers. These registers reside in modules
0 to 5. The following provides information about the spe-
cific module in which each peripheral resides:
• Module 0: Timer and Counter 1, GPIO Ports 0, 1, and 2
• Module 1: I²C Master, GPIO Port 6, SPIK Slave, Flash
Memory Controls
• Module 2: I²C Slave, Analog-to-Digital Converter
(ADC), Sample/Hold, Temperature, 3-Wire Master
• Module 3: Timer and Counter 2, MAC-Related Registers
• Module 4: Digital-to-Analog Converter (DAC)
• Module 5: Quick Trips, SPI Master, PWM
Memory Organization
The device incorporates several memory areas:
• 32KWords of flash memory for application program
storage
• 1KWord of SRAM for storage of temporary variables
• 4KWords of utility ROM contain a debugger and pro-
gram loader
• 16-level stack memory for storage of program return
addresses and general-purpose use
The memory is implemented using the Harvard archi-
tecture, with separate address spaces for program
memory, data memory, and register space. A pseudo-
Von Neumann memory map is also used, placing ROM,
application code, and data memory into a single contigu-
ous memory map. The pseudo-Von Neumann memory
map allows data memory to be mapped into program
space, permitting code execution from data memory.
In addition, program memory can be mapped into data
space, permitting code constants to be accessed as
data memory. Figure 6 shows the DS4830’s memory map
when executing from program memory space. Refer to
the DS4830 User’s Guide for memory map information
when executing from data or ROM space.
The incorporation of flash memory allows field upgrade of
the firmware. Flash memory can be password protected
with a 16-word key, denying access to program memory
by unauthorized individuals.
Utility ROM
The utility ROM is a 4KWord block of internal ROM
memory that defaults to a starting address of 8000h. The
utility ROM consists of subroutines that can be called
from application software, which includes the following:
• In-system programming (bootstrap loader) over JTAG
or I²C-compatible interfaces
• In-circuit debug routines
MAXQ is a registered trademark of Maxim Integrated Products, Inc.
SPI is a trademark of Motorola, Inc.
���������������������������������������������������������������� Maxim Integrated Products   17