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Initial scaffolding for paged memory

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This commit is contained in:
Jeff Parsons 2015-04-28 17:45:29 -07:00 • committed by jeffpar
commit 6108fb25ab
8 changed files with 431 additions and 276 deletions
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32
modules/pcjs/lib/fdc.js
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@ -861,7 +861,7 @@ FDC.prototype.initDrive = function(drive, iDrive, data)
/*
* resCode used to be an FDC global, but in order to insulate FDC state from the operation of various functions
* that operate on drive objects (eg, readByte and writeByte), I've made it a per-drive variable. This choice,
* that operate on drive objects (eg, readData and writeData), I've made it a per-drive variable. This choice,
* similar to my choice for handling PCN, may be contrary to how the actual hardware works, but I prefer this
* approach, as long as it doesn't expose any incompatibilities that any software actually cares about.
*/
@ -1110,7 +1110,7 @@ FDC.prototype.copyDrive = function(iDrive)
*
* Also note that in an actual FDC request, drive.nBytes is initialized to the size of a single sector; the extent
* of the entire transfer is actually determined by a count that has been pre-loaded into the DMA controller. The FDC
* isn't even aware of the extent of the transfer, so in the case of a read request, all readByte() can do is return
* isn't even aware of the extent of the transfer, so in the case of a read request, all readData() can do is return
* bytes until the current track (or, in the case of a multi-track request, the current cylinder) has been exhausted.
*
* Since seekDrive() is for use with non-DMA requests, we use nBytes to specify the length of the entire transfer.
@ -1144,7 +1144,7 @@ FDC.prototype.seekDrive = function(drive, iSector, nSectors)
drive.resCode = FDC.REG_DATA.RES.NONE;
/*
* At this point, we've finished simulating what an FDC.REG_DATA.CMD.READ_DATA command would have performed,
* up through doRead(). Now it's the caller responsibility to call readByte(), just like the DMA Controller would.
* up through doRead(). Now it's the caller responsibility to call readData(), just like the DMA Controller would.
*/
return true;
}
@ -2147,7 +2147,7 @@ FDC.prototype.pushST3 = function(drive)
FDC.prototype.dmaRead = function(drive, b, done)
{
if (b === undefined || b < 0) {
this.readByte(drive, done);
this.readData(drive, done);
return;
}
/*
@ -2168,7 +2168,7 @@ FDC.prototype.dmaRead = function(drive, b, done)
FDC.prototype.dmaWrite = function(drive, b)
{
if (b !== undefined && b >= 0)
return this.writeByte(drive, b);
return this.writeData(drive, b);
/*
* The DMA controller should be GIVING us data, not ASKING for data; this suggests an internal DMA miscommunication
*/
@ -2285,7 +2285,7 @@ FDC.prototype.doFormat = function(drive)
};
/**
* readByte(drive, done)
* readData(drive, done)
*
* The following drive properties must have been setup prior to our first call:
*
@ -2294,11 +2294,11 @@ FDC.prototype.doFormat = function(drive)
* drive.bSector
* drive.sector (initialized to null)
*
* On the first readByte() request, since drive.sector will be null, we ask the Disk object to look
* On the first readData() request, since drive.sector will be null, we ask the Disk object to look
* up the first sector of the request. We then ask the Disk for bytes from that sector until the sector
* is exhausted, and then we look up the next sector and continue the process.
*
* NOTE: Since the FDC isn't aware of the extent of the transfer, all readByte() can do is return bytes
* NOTE: Since the FDC isn't aware of the extent of the transfer, all readData() can do is return bytes
* until the current track (or, in the case of a multi-track request, the current cylinder) has been exhausted.
*
* TODO: Research the requirements, if any, for multi-track I/O and determine what else needs to be done.
@ -2307,7 +2307,7 @@ FDC.prototype.doFormat = function(drive)
* @param {Object} drive
* @param {function(number,boolean,Object,number)} done (number is next available byte from drive, or -1 if no more bytes available)
*/
FDC.prototype.readByte = function(drive, done)
FDC.prototype.readData = function(drive, done)
{
var b = -1;
var obj = null, off = 0; // these variables are purely for BACKTRACK purposes
@ -2332,7 +2332,7 @@ FDC.prototype.readByte = function(drive, done)
drive.ibSector = 0;
/*
* We "pre-advance" bSector et al now, instead of waiting to advance it right before the seek().
* This allows the initial call to readByte() to perform a seek without triggering an unwanted advance.
* This allows the initial call to readData() to perform a seek without triggering an unwanted advance.
*/
this.advanceSector(drive);
} while (true);
@ -2341,7 +2341,7 @@ FDC.prototype.readByte = function(drive, done)
};
/**
* writeByte(drive, b)
* writeData(drive, b)
*
* The following drive properties must have been setup prior to our first call:
*
@ -2350,11 +2350,11 @@ FDC.prototype.readByte = function(drive, done)
* drive.bSector
* drive.sector (initialized to null)
*
* On the first writeByte() request, since drive.sector will be null, we ask the Disk object to look
* On the first writeData() request, since drive.sector will be null, we ask the Disk object to look
* up the first sector of the request. We then send the Disk bytes for that sector until the sector
* is full, and then we look up the next sector and continue the process.
*
* NOTE: Since the FDC isn't aware of the extent of the transfer, all writeByte() can do is accept bytes
* NOTE: Since the FDC isn't aware of the extent of the transfer, all writeData() can do is accept bytes
* until the current track (or, in the case of a multi-track request, the current cylinder) has been exhausted.
*
* TODO: Research the requirements, if any, for multi-track I/O and determine what else needs to be done.
@ -2364,7 +2364,7 @@ FDC.prototype.readByte = function(drive, done)
* @param {number} b containing next byte to write
* @return {number} (b unchanged; return -1 if command should be terminated)
*/
FDC.prototype.writeByte = function(drive, b)
FDC.prototype.writeData = function(drive, b)
{
if (drive.resCode || !drive.disk) return -1;
do {
@ -2387,7 +2387,7 @@ FDC.prototype.writeByte = function(drive, b)
drive.ibSector = 0;
/*
* We "pre-advance" bSector et al now, instead of waiting to advance it right before the seek().
* This allows the initial call to writeByte() to perform a seek without triggering an unwanted advance.
* This allows the initial call to writeData() to perform a seek without triggering an unwanted advance.
*/
this.advanceSector(drive);
} while (true);
@ -2441,7 +2441,7 @@ FDC.prototype.writeFormat = function(drive, b)
this.printMessage("writeFormat(head=" + str.toHexByte(drive.bHead) + ",cyl=" + str.toHexByte(drive.bCylinder) + ",sec=" + str.toHexByte(drive.bSector) + ",len=" + str.toHexWord(drive.nBytes) + ")");
}
for (var i = 0; i < drive.nBytes; i++) {
if (this.writeByte(drive, drive.bFiller) < 0) {
if (this.writeData(drive, drive.bFiller) < 0) {
return -1;
}
}