Programmable array logic
Programmable Array Logic (called PAL forshort) are electronic semiconductor components in the field of digital technology which, through programming, receive a logical link structure between the input signals and the output signals. An alternative German term was also " programmable cell logic ". They were developed in 1978 by Monolithic Memories Inc. (MMI) and produced in the following years. PALs wereprogrammedin one of the first hardware description languages, PALASM . AMD launched the PAL AMPAL22V10 (22V10) in 1983. According to the data book, theGerman Philips subsidiary Valvo manufactured programmable integrated logic circuits in 1984. In 1986, the more universal PLAs had largely displaced the PALs, which were technically older in terms of development, from the semiconductor market.
PALs are special cases of PLAs ( Programmable Logic Arrays ) and are characterized by the fact that only their AND array can be programmed. PALs can only be written to once, since the links on the chip are created as part of the programming process by means of "burning through connections", the so-called antifuse technology . The programming is usually done in JEDEC format .
A further development of the PALs and PLAs are GALs (Generic Array Logic) and the CPLDs (Complex Programmable Logic Device), which are still more recent but more complex in terms of development.
Since the mid-1990s, PALs and GALs have rarely been used in newly developed circuits and have been almost completely replaced by Complex Programmable Logic Devices (CPLDs). CPLDs have no restrictions regarding the usability of the AND / OR matrices in the entrance area, can be programmed and erased electronically, can be programmed, like Field Programmable Gate Arrays (FPGAs), in standardized hardware programming languages such as VHDL , and they also include a specific one Number of registers .
- formerly Monolithic Memories Inc. , USA
- formerly Valvo GmbH, Germany
- formerly Philips GmbH, Netherlands
- formerly Texas Instruments , USA
- formerly AMD , USA
- formerly National Semiconductor , USA
- formerly Lattice
- formerly Cypress Semiconductor Corporation
Generic Array Logic (GAL)
As a further development of the PALs, the Lattice Semiconductor Corporation first brought the rewritable Generic Array Logic ( GAL for short ) modules onto the market. They consist of a programmable AND matrix and a hard-wired OR matrix. In contrast to the PAL, they can be written on electrically and erased either by UV light ( EPLD ) or electrically (EEPLD), which makes reprogramming possible.
The name GAL is a trademark of the Lattice company, which means that there are some companies that use their original names to designate these modules under license, and other companies that have renamed these modules (at AMD, for example, under the name PALCE) - the programming algorithm differs here but not the pin assignment and function.
The designation indicates in the sample what kind of logic module it is and provides information about its properties. A GAL16v8 is a GAL component with 16 matrix inputs for the logic matrix, output type v (variable architecture) and has eight outputs. Then, after a minus, there is the gate delay in ns and further information about operating temperatures and the chip housing .
GAL modules have three different operating modes, which are defined by two architecture bits during programming. A third bit sets the function for outputs whether they should function as an input or output (AC1 (n), n = pin number). This means that in general every output can also be used as an input. The simple mode (SYN = 1, AC0 = 0) enables the GAL block to be used as a simple logic gate , with linking of the AND blocks with subsequent OR blocks. The complex mode (SYN = 1, AC0 = 1) allows multiplexing with the help of tri-state outputs and the last of the modes, the register mode, enables logic gates to be connected to registers using integrated D flip-flops . This means that even smaller, more complex circuits can be built without having to constantly expand the circuits with additional external logic modules.
At the end of 1988 SGS-Thomson brought GALs onto the market according to the data book mentioned.
Since the mid-1990s, PALs and GALs have rarely been used in newly developed circuits and have been almost completely replaced by Complex Programmable Logic Devices (CPLDs).
Manufacturer of GALs:
Since the mid-1990s, PALs / PLAs and GALs have hardly been used in newly developed circuits and have been almost completely replaced by the more complexly structured Complex Programmable Logic Devices (CPLDs). CPLDs have no restrictions regarding the usability of the AND / OR matrices in the entrance area, can be programmed and erased electronically, can be programmed, like Field Programmable Gate Arrays (FPGAs), in standardized hardware programming languages such as VHDL , and they also include a specific one Number of registers . see: Complex Programmable Logic Device
According to Böhmer, CPLD still belongs to the group of PAL / PLA / PLD (Programmable Logic Device) and GAL, but has a more complicated internal structure in the IC. The even newer FPGAs, however, belong to a different technology.
PIN compatibility and naming of PALs and GALs
The designation 16L8 of the PAL means that it has 16 inputs and 8 outputs with negative output logic (L = "Low" as output logic ). An H instead of the L stands for positive output logic. An R stands for use as a register (memory for binary numbers).
The older GALs from Lattice are pin-compatible with the much older PALs. Instead of the PAL "16L8", the GAL "16V8" from Lattice can be used. This also has 16 inputs and 8 outputs.
- PAL16R4 ... (short: 16R4) from Texas Instruments
- PAL16R6CN (short: 16R6) from MMI, 20PIN DIP, since 1978
- PAL16R8BCN (short: 16R8) from MMI, 20PIN DIP
- PAL16L8 ... (short: 16L8) from MMI, 20PIN DIP
- AMPAL22V10APC (short: 22V10) from AMD, 24PIN DIP, since 1983
- TI16L8-25 (short: 16L8), Filipino producer
- 16X4, manufacturer?
- PALCE16V8H-25JC (short: 16V8H) from AMD, 20PIN DIP
- PALCE16V8Z-12PI (short: 16V8Z) from AMD, 20PIN DIP
- PALCE16V8H-25 (short: 16V8H) from AMD, 20PIN DIP
- PALCE 16V8H-25JC / 4 (short: 16V8H) from AMD, 20PIN (4x5PINs)
- PAL / PLE device. Programmable Logic Array Handbook . 5th edition. Monolithic Memories, 1986 ( archive.org ).
- Ton Zengerink: PAL practice: dealing with the modern programmable logic modules . Franzis, Munich 1987, ISBN 3-7723-8551-6 .
- Advanced Micro Devices (Ed.): PAL Device Handbook . 1988 ( archive.org [accessed January 3, 2020]).
- Advanced Micro Devices (Ed.): PAL Device Data Book . 1988.
- Programmable Logic Manual - GAL Products. SGS-Thomson, 1988.
- Dieter Bitterle: GALs, programmable logic modules in theory and practice. 2nd edition, Franzis-Verlag, Munich 1992, ISBN 3-7723-5903-5 .
- Dieter Bitterle: Circuit technology with GALs, over 50 circuits for practical use. Franzis-Verlag, Munich 1992, ISBN 3-7723-4681-2 .
- Erwin Böhmer, Dietmar Ehrhardt, Wolfgang Oberschelp: Elements of applied electronics. 15th edition, Vieweg Verlag, Wiesbaden 2007, ISBN 978-3-8348-9021-4 , chapter ROMs, PROMs and PLDs , pp. 268–269, structure and programming of GALs in the appendix, pp. 418–419.
- Integrated programmable logic circuits. Data book. Valvo GmbH, 1984.
- Programmable Logic Devices Databook & Design Guide . National Semiconductor, 1990 ( archive.org [accessed January 3, 2020]).
- A. Auer: Programmable logic IC, properties, application, programming. Hüthig Buch, Heidelberg 1990, ISBN 3778519107 (Structure and programming of Programmable Logic Device (PLD), Generic Array Logic (GAL), Modifiable Gate Arrangement (AGA) and Logic Cell Array (LCA)).
- Geoff Bostock: Programmable logic handbook . 2nd Edition. Butterworth Heinemann, Oxford / Boston 1993, ISBN 0-7506-0808-0 .
- Computer History Museum timeline / 1978-PAL on computerhistory.org (English)
- Data sheet from PAL ICs on ti.com (March 1992, English)
- Manfred Seifart: "Principle structure of a PLA", In: "Digitale Schaltungen", VEB Verlag Technik Berlin, GDR, Berlin 1986, second edition, ISBN 3-341-00148-4 ., PROM PLA and PAL on p. 273
- Monolithic Memories announces: a revolution in logic design . In: Hayden Publishing (Ed.): Electronic Design . 26, No. 6, Rochelle, NJ, March 18, 1978, pp. 148B to 148C. Introductory advertisement on PAL (Programmable Array Logic).
- "Integrated programmable logic circuits. Data book." Valvo GmbH, 1984
- Manfred Seifart: "Principle structure of a PLA", In: "Digital circuits", VEB Verlag Technik Berlin, GDR, Berlin 1986, second edition, ISBN 3-341-00148-4 , p. 273
- "Programmable Logic Manual - GAL Products", First Edition, October 1988, SGS-Thomson
- Erwin Böhmer / Dietmar Ehrhardt / Wolfgang Oberschelp: Elements of Applied Electronics, Vieweg Verlag Wiesbaden, 2007, 15th edition, comments on PAL / PLD / GAL / CPLD p. 418
- Erwin Böhmer: Elements of applied electronics, Vieweg Verlag Wiesbaden, 1996, 10th edition, chapter "ROM, PLD and PAL" p. 269