DS1WM Datasheet, PDF (1/15 Pages) Dallas Semiconductor – Synthesizable 1-Wire Bus Master

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DS1WM
Synthesizable 1-Wire Bus Master
FEATURES
§ Memory maps into any standard byte-wide
data bus.
§ Eliminates CPU “bit-banging” by internally
generating all 1-Wire^® timing and control
signals.
§ Generates interrupts to provide for more
efficient programming.
§ Search ROM Accelerator relieves CPU from
any single bit operations on the 1-Wire Bus.
§ Supports Overdrive mode and slave
interrupts.
§ Capable of running off any system clock from
3.2MHz to 128MHz.
§ Small size: all digital design, only 1500 gates.
§ Available in both Verilog and VHDL.
§ Applications include any circuit containing a
1-Wire communication bus.
Customer ASIC
Internal
Data Bus
Interrupt
1-Wire
Master
1-Wire
Bus
DESCRIPTION
As more 1-Wire devices become available, more and more users have to deal with the demands of
generating 1-Wire signals to communicate to them. This usually requires “bit-banging” a port pin on a
microprocessor, and having the microprocessor perform the timing functions required for the 1-Wire
protocol. While 1-Wire transmission can be interrupted mid-byte, it cannot be interrupted during the
“low” time of a bit time slot; this means that a CPU will be idled for up to 60 microseconds for each bit
sent and at least 480 microseconds when generating a 1-Wire reset. The 1-Wire Master helps users handle
communication to 1-Wire devices in their system without tying up valuable CPU cycles. Integrated into a
user’s ASIC as a 1-Wire port, the core is available in both VHDL and Verilog code and uses very little
chip area (1492 gates plus 1 bond pad for the Verilog version).
This circuit is designed to be memory mapped into the user’s system and provides complete control of the
1-Wire bus through 8 bit commands. The host CPU loads commands, reads and writes data, and sets
interrupt control through five individual registers. All of the timing and control of the 1-Wire bus are
generated within. The host merely needs to load a command or data and then may go on about its
business. When bus activity has generated a response that the CPU needs to receive, the 1-Wire Master
sets a status bit and, if enabled, generates an interrupt to the CPU. In addition to write and read
simplification, the 1-Wire Master also provides a Search ROM Accelerator function relieving the CPU
from having to perform any single-bit operations on the 1-Wire bus.
1-Wire is a registered trademark of Dallas Semiconductor.
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