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Bit
1 4 8 12 16 18 24 26 31 32 36 48 60 64 128 256 512
Application
16 32 64
Floating point precision
×½ ×1 ×2 ×4
Floating point decimal precision
32 64 128

In computer architecture, 18-bit integers, memory addresses, or other data units are those that are at most 18 bits (2.25 octets) wide. Also, 18-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size.

18 binary digits have 262144 (1000000 octal, 40000 hexadecimal) distinct combinations.

18 bits was a common word size for smaller computers in the 1960s, when large computers often used 36 bit words and 6-bit character sets were the norm.

Example computer architectures[edit]

Possibly the most well-known 18-bit computer architectures are the PDP-1, PDP-4, PDP-7, PDP-9 and PDP-15 minicomputers produced by Digital Equipment Corporation from 1960 to 1975.

The UNIVAC produced several 18-bit computers, including the UNIVAC 418 and several military systems.

The IBM 7700 Data Acquisition System was announced by IBM on December 2, 1963.

The BCL Molecular 18 was a group of systems designed and manufactured in the UK in the 1970s and 1980s.

The NASA Standard Spacecraft Computer NSSC-1 was developed as a standard component for the MultiMission Modular Spacecraft at the Goddard Space Flight Center (GSFC) in 1974.

The flying-spot store digital memory in the first experimental electronic switching systems used nine plates of optical memory that were read and written two bits at a time, producing a word size of 18 bits.

Character encoding[edit]

18-bit machines use a variety of character encodings.

The DEC Radix-50, called Radix 508 format, packs three characters plus two bits in each 18-bit word.[1]

The Teletype packs three characters in each 18-bit word; each character a 5-bit Baudot code and an upper-case bit.[2]

The DEC SIXBIT format packs three characters in each 18-bit word,[2] each 6-bit character obtained by stripping the high bits from the 7-bit ASCII code, which folds lowercase to uppercase letters.

References[edit]

  1. ^ Digital Equipment Corporation, PDP-9 Utility Programs--Advanced Software System--Programmer's Reference Manual, full text, Digital Equipment Corporation, 1968, Appendix 1.
  2. ^ a b "PDP-7 Symbolic Assembler Programming Manual". p. 6; p. 38-39.

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/18-bit — Please support Wikipedia.
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1273 news items

EE Times

EE Times
Fri, 05 Feb 2016 15:03:45 -0800

Apparently, this little scamp boasts 8/9/16/18 bit MCU, 3/4 wire SPI, and 16/18 bit RGB interface options along with 300 NITS. Now all I have to do is work out what all of this means in my version of the real world (is 300 NITS enough -- would 301 NITS ...

Power Electronics Technology

Power Electronics Technology
Wed, 23 Sep 2015 16:26:15 -0700

Linear Technology Corp. recently introduced the LTC2348-18, an 18-bit, 8-channel simultaneous sampling successive approximation register (SAR) analog-to digital converter (ADC). While converting eight channels at 200ksps per channel throughput, each ...

IHS Electronics360

IHS Electronics360
Fri, 04 Dec 2015 07:40:09 -0800

Dresden, Germany-based chipmaker ZDM AG (ZMDI) has introduced an 18-bit sensor signal conditioner (SSC) targeted at high-resolution sensor module applications. The sensor signal can be used in portable navigation systems, industrial pressure sensing ...

ThomasNet News (press release) (blog)

ThomasNet News (press release) (blog)
Mon, 18 Jan 2016 06:15:00 -0800

Its dual 18-bit high speed digitizers facilitate measuring actual device operation that can be graphically displayed right on the front panel for for immediate analysis. Based on the successful 2450 and 2460 SMU platforms, the 2461 features the highest ...
 
Marketwired (press release)
Tue, 01 Dec 2015 13:22:30 -0800

ZMD AG (ZMDI), an award-winning global semiconductor company headquartered in Dresden, Germany, and specializing in enabling energy-efficient solutions, today announces the new ZSSC3018 High-Resolution 18-Bit Sensor Signal Conditioner (SSC).
 
ThomasNet News (press release) (blog)
Fri, 15 Jan 2016 06:15:00 -0800

This robust, stand alone, low-power data logger features USB memory stick support, 18-bit resolution, extensive communications capabilities and a built-in display. The DT80 also offers support for Modbus for SCADA systems, FTP and Web interface, and ...
 
Consumer Electronics Net
Wed, 13 Jan 2016 06:03:45 -0800

Its dual 18-bit high speed digitizers facilitate measuring actual device operation that can be graphically displayed right on the front panel for for immediate analysis. Based on the successful 2450 and 2460 SMU platforms, the 2461 features the highest ...

CTIMES

CTIMES
Thu, 01 Oct 2015 02:09:54 -0700

Linear Technology Corporation introduces the LTC2387-18, an ultrafast 15Msps, 18-bit successive approximation register (SAR) analog-to-digital converter (ADC) with no cycle latency and no pipeline delay.
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