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Commodore Bus
The Commodore serial IEEE-488 bus (IEC Bus), is Commodore's interface for primarily magnetic disk data storage and printers for Commodore 8-bit home computers: the VIC-20, Commodore 64, Commodore 128, Plus/4, Commodore 16, and Commodore 65. Description and history The parallel IEEE-488 interface used on the Commodore PET (1977) computer line was too costly, so a cost reduced version was developed, which consisted of a stripped down, serial version of the IEEE-488 interface, with only a few signals remaining; however, the general protocol layout was kept. Commodore began using this bus with the VIC-20 (1980). Connection to the computer utilizes a DIN-6 connector (DIN 45322). Transfer speed Interface Protocol description The bus signals are digital single-ended open collector TTL and active when low. Bus devices have to provide their own power. Because the bus lines are electrically open collector it works like a long OR gate between all device line drivers. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEEE-488
IEEE 488 is a short-range digital communications 8-bit parallel multi-master interface bus specification developed by Hewlett-Packard as HP-IB (Hewlett-Packard Interface Bus). It subsequently became the subject of several standards, and is generically known as GPIB (General Purpose Interface Bus). Although the bus was created in the late 1960s to connect together automated test equipment, it also had some success during the 1970s and 1980s as a peripheral bus for early microcomputers, notably the Commodore PET. Newer standards have largely replaced IEEE 488 for computer use, but it is still used by some test equipment. Origins In the late 1960s, Hewlett-Packard (HP) manufactured various automated test and measurement instruments, such as digital multimeters and logic analyzers. They developed the ''HP Interface Bus (HP-IB)'' to enable easier interconnection between instruments and controllers (computers and other instruments). The bus was relatively easy to implemen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commodore 65
The Commodore 65 (also known as the C64DX) is a prototype computer created at Commodore Business Machines in 1990–1991. It is an improved version of the Commodore 64, and it was meant to be backwards-compatible with the older computer, while still providing a number of advanced features close to those of the Amiga. History In September 1989 ''Compute!'s Gazette'' noted that "Sales of the 64 have diminished rapidly, Nintendo has eaten big holes in the market, and the life of the old warhorse computer should somehow be extended." Noting that Apple had developed the IIGS to extend the life of its Apple II series, the magazine asked "Will Commodore take the same tack?", then continued: The ''Gazette'' added, "Our sources also report that there is a great deal of infighting at Commodore as to whether the machine should be released. The sales staff wants to get the machine out the door, while the naysaying engineers have dubbed it 'son of Plus/4.'" While the next ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KERNAL
KERNAL is Commodore's name for the ROM-resident operating system core in its 8-bit home computers; from the original PET of 1977, followed by the extended but strongly related versions used in its successors: the VIC-20, Commodore 64, Plus/4, C16, and C128. Description The Commodore 8-bit machines' KERNAL consists of the low-level, close-to-the-hardware OS routines roughly equivalent to the BIOS in IBM PC compatibles (in contrast to the BASIC interpreter routines, also located in ROM) as well as higher-level, device-independent I/O functionality, and is user-callable via a jump table in RAM whose central (oldest) part, for reasons of backwards compatibility, remains largely identical throughout the whole 8-bit series. The KERNAL ROM occupies the last 8 KB of the 8-bit CPU's 64 KB address space ($E000–$FFFF). The jump table can be modified to point to user-written routines, for example rewriting the screen display routines to display animated graphics or copying the charac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OR Gate
The OR gate is a digital logic gate that implements logical disjunction. The OR gate returns true if either or both of its inputs are true; otherwise it returns false. The input and output states are normally represented by different voltage levels. Description The gate accepts two inputs. It outputs a 1 if either or both of these inputs are 1, or outputs a 0 only if both inputs are 0. The inputs and outputs are binary digits (" bits") which have two possible logical states. In addition to 1 and 0, these states may be called true and false, high and low, active and inactive, or other such pairs of symbols. Thus it performs logical disjunction (∨) from mathematical logic. The gate can be represented with the plus sign (+) because it can be used for logical addition. Equivalently, an OR gate finds the ''maximum'' between two binary digits, just as the AND gate finds the ''minimum''. Together with the AND gate and the NOT gate, the OR gate is one of three basic logic gate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transistor–transistor Logic
Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors. Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor"), as opposed to earlier resistor–transistor logic (RTL) and diode–transistor logic (DTL). TTL integrated circuits (ICs) were widely used in applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, and synthesizers. After their introduction in integrated circuit form in 1963 by Sylvania Electric Products, TTL integrated circuits were manufactured by several semiconductor companies. The 7400 series by Texas Instruments became particularly popular. TTL manufacturers offered a wide range of logic gates, flip-flops, counters, and other circuits. Variations of the original TTL circuit design offered higher speed or lower power dissipation to allow design optimization. TTL devices were original ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Collector
An open collector is a common type of output found on many integrated circuits (IC), which behaves like a switch that is either connected to ground or disconnected. Instead of outputting a signal of a specific voltage or current, the output signal is applied to the base of an internal NPN transistor whose collector is externalized (open) on a pin of the IC. The emitter of the NPN transistor is connected internally to the ground pin. If the output device is a MOSFET the output is called open drain and it functions in a similar way. For example, the I²C bus and 1-Wire bus are based on this concept. Function In the picture, the transistor base is labeled "IC output". This is a signal from the internal IC logic to the transistor. This signal controls the transistor switching. The external output is the transistor collector; the transistor forms an interface between the internal IC logic and parts external to the IC. On schematic component symbols, the open output is indicated wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-ended Signaling
Single-ended signaling is the simplest and most commonly used method of transmitting electrical signals over wires. One wire carries a varying voltage that represents the signal, while the other wire is connected to a reference voltage, usually ground. The main alternative to single-ended signaling is called ''differential signaling'' where the two conductors carry signals equal in magnitude but of opposite electric polarity. Single-ended signaling is less expensive to implement than differential, but it has a distinct disadvantage: a single-ended system requires a power supply voltage equal to the maximum amplitude of the signal to be received whereas a differential system only requires a voltage half of the signal amplitude to be received. For a given power supply voltage then, a differential system produces signals of twice the amplitude and therefore has twice as good noise immunity (6 dB higher signal-to-noise ratio) as a single-ended system. The main advantage of single-end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commodore 1571
The Commodore 1571 is Commodore's high-end 5¼" floppy disk drive, announced in the summer of 1985. With its double-sided drive mechanism, it has the ability to use double-sided, double-density (DS/DD) floppy disks, storing a total of 360 kB per floppy. It also implemented a "burst mode" that doubled transfer speeds, helping address the very slow performance of previous Commodore drives. Earlier Commodore drives used a custom group coded recording format that stored 170 kB per side of a disk. This made it fairly competitive in terms of storage, but limited it to only reading and writing disks from other Commodore machines. The 1571 was designed to partner with the new Commodore 128 (C128), which introduced support for CP/M. Adding double-density MFM encoding allowed the drive to read and write contemporary CP/M disks (and many others). In contrast to its single-sided predecessors, the 1541 and the briefly-available 1570, the 1571 can use both sides of the disk a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epyx
Epyx, Inc. was a video game developer and publisher active in the late 1970s and 1980s. The company was founded as Automated Simulations by Jim Connelley and Jon Freeman, originally using Epyx as a brand name for action-oriented games before renaming the company to match in 1983. Epyx published a long series of games through the 1980s. The company is currently owned by Bridgestone Multimedia Group Global. History Formation In 1977, Susan Lee-Merrow invited Jon Freeman to join a Dungeons & Dragons game hosted by Jim Connelley and Jeff Johnson. Connelley later purchased a Commodore PET computer to help with the bookkeeping involved in being a dungeon master, and came up with the idea of writing a computer game for the machine before the end of the year so he could write it off on his taxes. Freeman had written on gaming for several publications, and joined Connelley in the design of a new space-themed wargame. Starting work around August 1978, Freeman wrote the basic rules, missio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast Loader
A fast loader is a software program for a home computer, such as the Commodore 64 or ZX Spectrum, that accelerates the speed of file loading from floppy disk or compact cassette. Floppy disks Fast loaders came about because of a discrepancy between the actual speed at which floppy drives could transfer data and the speed that was provided by the operating system's default routines. This discrepancy was most pronounced on the VIC-20 and Commodore 64. While the earlier Commodore PET series had used an industry-standard IEEE-488 parallel bus, this was replaced with a custom Commodore serial bus on the VIC-20. The serial bus was intended to be nearly as fast as its predecessor, due to the use of the 6522 VIA as a hardware shift register on both the drive and computer. However, hardware bugs were discovered in the 6522 that prevented this function from working consistently. As a result, the KERNAL ROM routines were hastily rewritten to transfer a single bit at a time, using ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commodore 1541
The Commodore 1541 (also known as the CBM 1541 and VIC-1541) is a floppy disk drive which was made by Commodore International for the Commodore 64 (C64), Commodore's most popular home computer. The best-known floppy disk drive for the C64, the 1541 is a single-sided 170-kilobyte drive for 5¼" disks. The 1541 directly followed the Commodore 1540 (meant for the VIC-20). The disk drive uses group coded recording (GCR) and contains a MOS Technology 6502 microprocessor, doubling as a disk controller and on-board disk operating system (DOS) processor. The number of sectors per track varies from 17 to 21 (an early implementation of zone bit recording). The drive's built-in disk operating system is CBM DOS 2.6. History Introduction The 1541 was priced at under at its introduction. A C64 plus a 1541 cost about $900, while an Apple II with no disk drive cost $1,295. The first 1541 drives produced in 1982 have a label on the front reading VIC-1541 and have an off-white case to m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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