PLD - Revision history

Phi2x: /* Comparison Table */

2024-09-27T17:27:04Z

Comparison Table

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	{\| class="wikitable"		{\| class="wikitable"
	\|-		\|-
	! Feature !! PAL !! GAL !! PLA !! ULA !! Gate Array		! Feature !! PAL / HAL !! GAL !! PLA !! ULA !! Gate Array
	\|-		\|-
	\| Flexibility \|\| Low \|\| Low-Medium \|\| Medium \|\| Medium \|\| Medium-High		\| Flexibility \|\| Low \|\| Low-Medium \|\| Medium \|\| Medium \|\| Medium-High

Phi2x: /* Simple Programmable Logic Device (SPLD) */

2024-09-27T17:18:46Z

Simple Programmable Logic Device (SPLD)

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	For example, the Amstrad CPC 6128 used a PAL to manage memory and bank switching, showing how these chips helped improve performance in small, affordable computers.		For example, the Amstrad CPC 6128 used a PAL to manage memory and bank switching, showing how these chips helped improve performance in small, affordable computers.

			<br>

			=== Hard Array Logic (HAL) ===

			MMI also offered a similar family called HAL, or "Hard Array Logic", which were like PAL devices except that they were mask-programmed at the factory.

			HAL and PAL have been used interchangeably by Amstrad.

	<br>		<br>

Phi2x: /* Programmable Array Logic (PAL) */

2024-09-27T16:52:59Z

Programmable Array Logic (PAL)

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	=== Programmable Array Logic (PAL) ===		=== Programmable Array Logic (PAL) ===

	PALs, introduced in 1978 by Monolithic Memories, became important in many 8-bit computers. They featured a programmable AND array and a fixed OR array, making them useful for handling simple logic tasks. PALs came in one-time programmable or UV-erasable versions, offering flexibility to developers.		PALs, introduced in 1978 by Monolithic Memories Inc (MMI), became important in many 8-bit computers. They featured a programmable AND array and a fixed OR array, making them useful for handling simple logic tasks. PALs came in one-time programmable or UV-erasable versions, offering flexibility to developers.

	One common use for PALs was address decoding, which enabled memory bank switching, allowing computers to access more memory than their basic design supported. PALs were also used to simplify communication between the CPU and peripherals.		One common use for PALs was address decoding, which enabled memory bank switching, allowing computers to access more memory than their basic design supported. PALs were also used to simplify communication between the CPU and peripherals.

Phi2x at 03:36, 22 September 2024

2024-09-22T03:36:07Z

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	In the late 1970s and early 1980s, both 8-bit home computers and Programmable Logic Devices (PLDs) started gaining popularity. As these technologies came together, they opened up exciting possibilities for using early PLD technology in the design of 8-bit computers. In this article, we'll take a look at the different types of PLDs that were important during this era, explore their features, and see how they were applied ~~in those early machines~~.		In the late 1970s and early 1980s, both 8-bit home computers and Programmable Logic Devices (PLDs) started gaining popularity. As these technologies came together, they opened up exciting possibilities for using early PLD technology in the design of 8-bit computers. In this article, we'll take a look at the different types of PLDs that were important during this era, explore their features, and see how they were applied.

	<br>		<br>

Phi2x at 03:35, 22 September 2024

2024-09-22T03:35:39Z

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	~~The~~ late 1970s and early 1980s ~~saw the rise of~~ both 8-bit home computers and Programmable Logic Devices (~~PLD~~). ~~This convergence led to interesting applications of~~ early PLD technology in 8-bit ~~computer design~~. ~~This~~ article ~~explores~~ the ~~various subtypes~~ of PLDs that were ~~relevant~~ during ~~the 8-bit computer~~ era, ~~comparing~~ their ~~characteristics~~ and ~~their use~~ in ~~these pioneering~~ machines.		In the late 1970s and early 1980s, both 8-bit home computers and Programmable Logic Devices (PLDs) started gaining popularity. As these technologies came together, they opened up exciting possibilities for using early PLD technology in the design of 8-bit computers. In this article, we'll take a look at the different types of PLDs that were important during this era, explore their features, and see how they were applied in those early machines.

	<br>		<br>

Phi2x: /* Summary */

2024-09-22T03:30:31Z

Summary

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	== Summary ==		== Summary ==

	~~The variety of PLD subtypes available during~~ the 8-bit computer ~~era provided~~ designers ~~with a range~~ of options for ~~implementing custom logic~~.		During the 8-bit computer days, there were all kinds of PLD (programmable logic device) subtypes that gave designers plenty of options for customizing their systems.

	From ~~simple~~ PALs used for address decoding to ~~complex~~ ULAs that ~~integrated~~ multiple system functions, these devices ~~were crucial~~ in ~~the evolution of~~ 8-bit computer design. They ~~allowed for~~ cost-effective ~~customization~~ and ~~helped drive~~ the home computer ~~revolution of~~ the 1980s.		From basic PALs used for things like address decoding, to more advanced ULAs that packed in multiple system functions, these devices played a key role in shaping 8-bit computer design. They were a cost-effective way to tweak systems and were a big part of the home computer boom in the 1980s.

	~~The legacy~~ of these early PLDs ~~can be seen~~ in ~~the complex programmable logic devices (CPLD)~~, ~~ASIC~~ and FPGAs ~~used in modern computing systems~~, which trace their ~~lineage~~ back to ~~these pioneering devices of~~ the 8-bit era.		You can still see the impact of these early PLDs in today’s more advanced chips like CPLDs, ASICs, and FPGAs, which all trace their roots back to the 8-bit era.

	[[Category:Hardware]] [[Category:Electronic Component]]		[[Category:Hardware]] [[Category:Electronic Component]]

Phi2x: /* Programmable Array Logic (PAL) */

2024-09-22T03:18:42Z

Programmable Array Logic (PAL)

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	=== Programmable Array Logic (PAL) ===		=== Programmable Array Logic (PAL) ===

	~~Introduced~~ by Monolithic Memories in ~~1978~~, PALs ~~quickly found applications~~ in 8-~~bit computer systems~~.		PALs, introduced in 1978 by Monolithic Memories, became important in many 8-bit computers. They featured a programmable AND array and a fixed OR array, making them useful for handling simple logic tasks. PALs came in one-time programmable or UV-erasable versions, offering flexibility to developers.

	~~Key characteristics:~~		One common use for PALs was address decoding, which enabled memory bank switching, allowing computers to access more memory than their basic design supported. PALs were also used to simplify communication between the CPU and peripherals.
	* Featured a programmable AND array followed by a fixed OR array
	* One~~-time programmable (OTP) or UV-erasable versions available~~
	* Relatively fast and ~~suitable for simple logic functions~~

	~~Applications:~~		For example, the Amstrad CPC 6128 used a PAL to manage memory and bank switching, showing how these chips helped improve performance in small, affordable computers.
	* Address decoding: PALs were often used to decode memory addresses, ~~allowing for memory bank switching, a common technique in 8-bit computers to expand beyond their native address space.~~
	* I/O interface logic: They simplified the ~~interface between the CPU and various peripherals.~~
	* Example: The CPC 6128 used a PAL ~~for part of its~~ memory ~~management~~ and bank switching ~~logic~~.

	<br>		<br>

Phi2x: /* Generic Array Logic (GAL) */

2024-09-22T03:16:15Z

Generic Array Logic (GAL)

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	=== Generic Array Logic (GAL) ===		=== Generic Array Logic (GAL) ===

	GALs, introduced in the mid-1980s, ~~came towards~~ the end of the 8-bit computer era but still found ~~applications~~ in later designs and modifications.		GALs were introduced in the mid-1980s, coinciding with the end of the 8-bit computer era, but they still found use in later designs and modifications. One of their main advantages was being electrically erasable and reprogrammable, which distinguished them from traditional PALs. This feature allowed developers to easily make adjustments without needing new chips.

	~~Key differences from PALs:~~		GALs were also often pin-compatible with PALs, making it easy to swap them in for prototyping and upgrades. This compatibility led to their popularity in various applications, especially where quick changes were needed.
	* Electrically erasable, allowing for reprogramming
	* Often pin-compatible with PALs, making them ~~popular~~ for prototyping and upgrades

	~~Applications:~~		In practice, GALs were frequently used for aftermarket upgrades and modifications to 8-bit computers. They allowed hobbyists and small companies to create custom expansions more easily, promoting innovation in computing. Overall, GALs played an important role in linking classic 8-bit systems with newer technology demands.
	* GALs were ~~often~~ used in aftermarket upgrades or modifications to ~~existing~~ 8-bit ~~computer designs~~.
	* They allowed hobbyists and small companies to create custom expansions more easily.

	<br>		<br>

Phi2x: /* Programmable Logic Array (PLA) */

2024-09-22T03:14:38Z

Programmable Logic Array (PLA)

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	== Programmable Logic Array (PLA) ==		== Programmable Logic Array (PLA) ==

	PLAs offered ~~more~~ flexibility than PALs but were less common in 8-bit computer designs due to higher cost and power consumption.		PLAs offered greater flexibility than PALs but were less common in 8-bit computer designs due to their higher cost and power consumption. They featured programmable AND and OR arrays, which allowed for the implementation of more complex logic functions in a single device.

	~~Distinguishing features:~~		Despite their limited use, PLAs were sometimes chosen for advanced 8-bit systems, particularly for tasks like instruction decoding. A notable example is the Commodore 64, which used a PLA for part of its chip select and memory mapping logic. This illustrated the PLA’s ability to manage complex logic efficiently.
	* Both AND and ~~OR arrays were programmable~~
	* Could implement more complex logic ~~functions in a single device~~

	~~Applications:~~		While not as widely adopted, PLAs highlighted the need for flexibility in computer design. They were valuable in specific applications where intricate functionality was required, showing their importance in the development of certain complex 8-bit systems.
	* While ~~less common~~, PLAs were ~~sometimes used~~ in ~~more~~ complex 8-bit ~~computer designs for tasks like instruction decoding.~~
	* Example: The Commodore 64 used a PLA for part of its chip select and memory mapping logic, demonstrating the device's ability to handle complex logic in a single chip.

	<br>		<br>

Phi2x: /* Uncommitted Logic Array (ULA) */

2024-09-22T03:10:03Z

Uncommitted Logic Array (ULA)

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	== Uncommitted Logic Array (ULA) ==		== Uncommitted Logic Array (ULA) ==

	ULAs ~~played a crucial role in several popular~~ 8-bit ~~computer designs, especially~~ in the UK.		ULAs were key to the design of 8-bit computers in the UK, allowing for cost-effective and efficient solutions. They used pre-fabricated silicon wafers with unconnected logic gates, which manufacturers could customize by adding metal interconnects during final production. This approach made semi-custom chips cheaper than fully custom ones.

	~~Key characteristics:~~		A prime example is the Ferranti ULA in the Sinclair ZX Spectrum, which handled video generation, memory management, and I/O control. This integration reduced the number of components needed, keeping costs low. Similarly, the Acorn BBC Micro featured a custom ULA that managed I/O and video timing.
	* Pre-fabricated silicon wafers with unconnected logic gates
	* Customization done by adding metal interconnects in ~~final manufacturing stages~~
	* Allowed for semi-custom chips at lower costs ~~than fully~~ custom ~~ICs~~

	~~Applications:~~		By combining multiple functions into a single chip, ULAs helped produce affordable home computers, making technology more accessible to many. Their introduction marked an important shift in computer design, driving the evolution of personal computing.
	* The most famous example is the Ferranti ULA used in the Sinclair ZX Spectrum. This single chip ~~handled various functions including video generation~~, ~~memory management~~, ~~and I/O control~~.
	* The Acorn BBC Micro also used a custom ULA for much of its I/O handling and video timing generation.

	~~ULAs allowed 8-bit~~ computer ~~manufacturers to create custom chips that integrated multiple functions~~, ~~reducing chip count and overall system cost. This was crucial in producing affordable home computers~~.

	<br>		<br>