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-rw-r--r--docs/source/techspecs/floppy.rst8
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diff --git a/docs/source/techspecs/floppy.rst b/docs/source/techspecs/floppy.rst
index 609e5c53013..39060d4eddf 100644
--- a/docs/source/techspecs/floppy.rst
+++ b/docs/source/techspecs/floppy.rst
@@ -23,7 +23,7 @@ The new floppy subsystem aims at emulating the behaviour of floppies and floppy
A floppy disk is a disc that stores magnetic orientations on their surface disposed in a series on concentric circles called tracks or cylinders [1]_. Its main characteristics are its size (goes from a diameter of around 2.8" to 8") , its number of writable sides (1 or 2) and its magnetic resistivity. The magnetic resistivity indicates how close magnetic orientation changes can happen and the information kept. That's one third of what defines the term "density" that is so often used for floppies (the other two are floppy drive head size and bit-level encoding).
-The magnetic orientations are always binary, e.g. they're one way or the opposite, there's no intermediate state. Their direction can either be tengentially to the track, e.g in the direction or opposite to the rotation, or in the case of perpendicular recording the direction is perpendicular to the disc surface (hence the name). Perpendicular recording allows for closer orientation changes by writing the magnetic information more deeply, but arrived late in the technology lifetime. 2.88Mb disks and the floppy children (Zip drives, etc) used perpendicular recording. For simulation purposes the direction is not important, only the fact that only two orientations are possible is. Two more states are possible though: a portion of a track can be demagnetized (no orientation) or damaged (no orientation and can't be written to).
+The magnetic orientations are always binary, e.g. they're one way or the opposite, there's no intermediate state. Their direction can either be tangentially to the track, i.e. in the direction of or opposite to the rotation, or in the case of perpendicular recording the direction is perpendicular to the disc surface (hence the name). Perpendicular recording allows for closer orientation changes by writing the magnetic information more deeply, but arrived late in the technology lifetime. 2.88Mb disks and the floppy children (Zip drives, etc.) used perpendicular recording. For simulation purposes the direction is not important, only the fact that only two orientations are possible is. Two more states are possible though: a portion of a track can be demagnetized (no orientation) or damaged (no orientation and can't be written to).
A specific position in the disk rotation triggers an index pulse. That position can be detected through a hole in the surface (very visible in 5.25" and 3" floppies for instance) or through a specific position of the rotating center (3.5" floppies, perhaps others). This index pulse is used to designate the beginning of the track, but is not used by every system. Older 8" floppies have multiple index holes used to mark the beginning of sectors (called hard sectoring) but one of them is positioned differently to be recognized as the track start, and the others are at fixed positions relative to the origin one.
@@ -70,7 +70,7 @@ In every cell there may or may not be a magnetic orientation transition, e.g. a
Of course protections play with that to make formats not reproducible by the system controller, either breaking the three-zeroes rule or playing with the cells durations/sizes.
-Bit endocing is then the art of transforming raw data into a cell 0/1 configuration that respects the two constraints.
+Bit encoding is then the art of transforming raw data into a cell 0/1 configuration that respects the two constraints.
2.3.1.2. FM encoding
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@@ -108,9 +108,9 @@ Other encodings exist, like M2FM, but they're very rare and system-specific.
2.3.1.6. Reading back encoded data
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-Writing encoded data is easy, you only need a clock at the appropriate frequency and send or not a pulse on the clock edges. Reading back the data is where the fun is. Cells are a logical construct and not a physical measurable entity. Rotational speeds very around the defined one (+/- 2% is not rare) and local perturbations (air turbulence, surface distance...) make the instant speed very variable in general. So to extract the cell values stream the controller must dynamically synchronize with the pulse train that the floppy head picks up. The principle is simple: a cell-sized duration window is build within which the presence of at least one pulse indicates the cell is a '1', and the absence of any a '0'. After reaching the end of the window the starting time is moved appropriately to try to keep the observed pulse at the exact middle of the window. This allows to correct the phase on every '1' cell, making the synchronization work if the rotational speed is not too off. Subsequent generations of controllers used a Phase-Locked Loop (PLL) which vary both phase and window duration to adapt better to wrong rotational speeds, with usually a tolerance of +/- 15%.
+Writing encoded data is easy: you only need a clock at the appropriate frequency and send or not a pulse on the clock edges. Reading back the data is where the fun is. Cells are a logical construct and not a physical measurable entity. Rotational speeds very around the defined one (±2% is not rare), and local perturbations (air turbulence, surface distance…) make the instantaneous speed very variable in general. So to extract the cell values stream, the controller must dynamically synchronize with the pulse train that the floppy head picks up. The principle is simple: a cell-sized duration window is built within which the presence of at least one pulse indicates the cell is a '1', and the absence of any a '0'. After reaching the end of the window, the starting time is moved appropriately to try to keep the observed pulse at the exact middle of the window. This allows the phase to be corrected on every '1' cell, making the synchronization work if the rotational speed is not too off. Subsequent generations of controllers used Phase-Locked Loops (PLLs) which vary both phase and window duration to adapt better to inaccuarate rotational speeds, usually with a tolerance of ±15%.
-Once the cell data stream is extracted decoding depends on the encoding. In the FM and MFM case the only question is to recognize data bits from clock bits, while in GCR the start position of the first group should be found. That second level of synchronization is handled at a higher level using patterns not found in a normal stream.
+Once the cell data stream is extracted, decoding depends on the encoding. In the FM and MFM case the only question is to recognize data bits from clock bits, while in GCR the start position of the first group should be found. That second level of synchronization is handled at a higher level using patterns not found in a normal stream.
2.3.2. Sector-level organization