The FD1771 was succeeded by many derivatives that were mostly software-compatible:
The FD1781 was designed for double density, but required external modulation and demodulation circuitry, so it could support MFM, M2FM, or other double-density encodings.[3][4]
The FD1791-FD1797 series added internal support for double density (MFM) modulation, compatible with the IBM System/34 disk format. They required an external data separator.[5]
The WD1761-WD1767 series were versions of the FD179x series rated for a maximum clock frequency of 1 MHz, resulting in a data rate limit of 125 kbit/s for single density and 250 kbit/s for double density, thus preventing them from being used for 8-in (200 mm) floppy drives or the later "high-density" 5.25-inch (133 mm) or 90 mm floppy drives.
The WD2791-WD2797 series added an internal data separator using an analog phase-locked loop, with some external passive components required for the VCO. They took a 1 MHz or 2 MHz clock and were intended for 8-inch (203 mm) and 5.25-inch (133 mm) drives.[6]
The WD1770, WD1772, and WD1773 added an internal digital data separator and write precompensator, eliminating the need for external passive components but raising the clock rate requirement to 8 MHz. They supported double density, despite the apparent regression of the part number, and were packaged in 28-pin DIP packages.[7]
The WD1772PH02-02 was a version of the chip that Atari fitted to the Atari STE which supported high density (500 kbit/s) operation. After production at WD could not be sustained, Atari decided to licence the design and modify it to get high density and extra density (1MBit/s) operation. The chip was codenamed "Ajax", had the number C302096 and was produced by Toshiba.[citation needed]
Compatible chips[edit]
Many compatible chips were available from other vendors:
FD179x series from SMC Microelectronics
MB887x series from Fujitsu
VL177x series from VLSI Technology.
Soviet КР1818ВГ93 was a WD1793 clone
These families were used in many microcomputers and home computers including the Radio Shack TRS-80, Acorn Electron, BBC Master, Atari ST, Acorn Archimedes and the SAM Coupé, as well as the +D and DISCiPLE disk interfaces for the Sinclair ZX Spectrum, the Commodore 157x/1581 for the Commodore 64 and the Atari XF551 for the Atari XL/XE.
---------- Post added at 23:03 ---------- Previous post was at 22:43 ----------
Блин - прозрел с WD1773 сейчас!
http://dev-docs.atariforge.org/files/WD177X-00.pdf
Программно ПОЛНОСТЬЮ совместимо с нашей ВГ93 НО!
Ног всего 28, питание ТОЛЬКО +5, и все цепи обработки сигнала ВСТРОЕНЫ ( то есть внутри стоит пред компенсация записи и полный детектор сигнала с цифровой ФАПЧ! ) фактически к дисководу ставятся только буферные элементы. А это минус корпуса 4 и плюс к считыванию старых дисков без шаманства - за счет ФАПЧ.
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