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Fixed the fallback logic for IOPAGE ranges where only byte handlers exist (ie, the readROMByte() case)

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This commit is contained in:
Jeff 2016-11-06 09:48:12 -08:00 • committed by Jeff Parsons
commit 8188554875
6 changed files with 489 additions and 468 deletions
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27
modules/pdp11/lib/bus.js
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@ -219,7 +219,7 @@ BusPDP11.IOHANDLER = {
* Unlike regular Memory blocks, IOPAGE accesses permit word accesses on ODD addresses; that works
* just fine by registering WORD handlers for the appropriate ODD addresses. For BYTE accesses, it
* depends. For CPU register addresses, addIOHandlers() installs special byte handlers that perform
* either a simple word read or write. Other addresses must be handled on case-by-case basis.
* either a simple word read or write. Other addresses must be handled on a case-by-case basis.
*
* TODO: Another small potential improvement would be for addIOHandlers() to install fallbacks for ALL
* missing handlers, in both the ODD and EVEN cases, so there's never a need to check each function index
@ -265,6 +265,13 @@ BusPDP11.IOController = {
if (afn) {
if (afn[BusPDP11.IOHANDLER.READ_WORD]) {
b = afn[BusPDP11.IOHANDLER.READ_WORD](addrMasked & ~0x1) >> 8;
} else if (afn[BusPDP11.IOHANDLER.READ_BYTE]) {
/*
* WARNING: This is an unusual fall-back, because we're trying to read an ODD byte
* access using a BYTE handler registered for EVEN bytes. But if that's all we've got,
* then presumably the handler is prepared for it (certainly, readROMByte() is).
*/
b = afn[BusPDP11.IOHANDLER.READ_BYTE](addrMasked)
}
}
}
@ -346,6 +353,13 @@ BusPDP11.IOController = {
w = afn[BusPDP11.IOHANDLER.READ_WORD]? afn[BusPDP11.IOHANDLER.READ_WORD](0) : 0;
afn[BusPDP11.IOHANDLER.WRITE_WORD]((w & 0xff) | (b << 8), addrMasked);
fWrite = true;
} else if (afn[BusPDP11.IOHANDLER.WRITE_BYTE]) {
/*
* WARNING: This is an unusual fall-back, because we're trying to write an ODD byte
* access using a BYTE handler registered for EVEN bytes. But if that's all we've got,
* then presumably the handler is prepared for it (certainly, writeROMByte() is).
*/
afn[BusPDP11.IOHANDLER.WRITE_BYTE](b, addrMasked);
}
}
}
@ -1239,7 +1253,7 @@ BusPDP11.prototype.restoreMemory = function(a)
* getMemorySize(type)
*
* NOTE: The original pdp11.js defined MAX_MEMORY as IOBASE_UNIBUS - 16384, where IOBASE_UNIBUS
* is 4Mb less 256Kb, and then subtracted another 16Kb so that BSD 2.9 could boot.
* is 4Mb less 256Kb, and then it subtracted another 16Kb so that BSD 2.9 could boot.
*
* @this {BusPDP11}
* @param {number} type is one of the MemoryPDP11.TYPE constants (only RAM is currently supported)
@ -1263,6 +1277,11 @@ BusPDP11.prototype.getMemorySize = function(type)
* relative to the starting IOPAGE address, but they can also be absolute; we simply mask all addresses with
* IOPAGE_MASK.
*
* CAVEATS: If a conflict is reported, a partial set of handlers may still have been added. There is no mechanism
* for removing handlers, since this is considered an initialization function. And finally, when a range of addresses
* is used, each successive address is advanced by 2, so if you really want to add a handler for a "+1" (usually odd)
* address, then you must add it individually.
*
* @this {BusPDP11}
* @param {number} start address
* @param {number} end address
@ -1319,8 +1338,8 @@ BusPDP11.prototype.addIOTable = function(component, table, msgCategory, sName)
var nRegs = afn[5] || 1;
/*
* As discussed in the IOController comments above, when handlers are being registered for the following
* addresses, we must install different fallback handlers for all BYTE accesses.
* As discussed in the IOController comments above, when handlers are being registered for these
* BYTE-granular UNIBUS addresses, we must install custom fallback handlers for all BYTE accesses.
*/
if (addr >= PDP11.UNIBUS.R0SET0 && addr <= PDP11.UNIBUS.R6USER) {
if (!fnReadByte && fnReadWord) {