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Simplify the Bus and Memory interfaces slightly, by enabling WORDBUS, which treats all word accesses as aligned; the CPU is has sole responsibility for detecting unaligned word addresses and trapping appropriatelu

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This commit is contained in:
Jeff 2016-10-06 14:17:29 -07:00 • committed by Jeff Parsons
commit 1a1614a648
12 changed files with 444 additions and 398 deletions
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21
modules/pdp11/lib/memory.js
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@ -782,10 +782,15 @@ MemoryPDP11.prototype = {
*/
readWordLE: function readWordLE(off, addr) {
/*
* TODO: It remains to be seen if there's any advantage to checking the offset for an aligned read
* vs. always reading the bytes separately.
* TODO: For non-WORDBUS machines, it remains to be seen if there's any advantage to checking the offset
* for an aligned read vs. always reading the bytes separately.
*/
var w = (off & 0x1)? (this.ab[off] | (this.ab[off+1] << 8)) : this.aw[off >> 1];
var w;
if (PDP11.WORDBUS || !(off & 0x1)) {
w = this.aw[off >> 1];
} else {
w = this.ab[off] | (this.ab[off+1] << 8);
}
if (DEBUGGER && this.dbg && this.dbg.messageEnabled(MessagesPDP11.MEM)) {
this.dbg.printMessage("Memory.readWord(" + this.dbg.toStrBase(addr) + "): " + this.dbg.toStrBase(w), true);
}
@ -840,14 +845,14 @@ MemoryPDP11.prototype = {
*/
writeWordLE: function writeWordLE(off, w, addr) {
/*
* TODO: It remains to be seen if there's any advantage to checking the offset for an aligned write
* vs. always writing the bytes separately.
* TODO: For non-WORDBUS machines, it remains to be seen if there's any advantage to checking the offset
* for an aligned write vs. always writing the bytes separately.
*/
if (off & 0x1) {
if (PDP11.WORDBUS || !(off & 0x1)) {
this.aw[off >> 1] = w;
} else {
this.ab[off] = w;
this.ab[off+1] = w >> 8;
} else {
this.aw[off >> 1] = w;
}
this.fDirty = true;
if (DEBUGGER && this.dbg && this.dbg.messageEnabled(MessagesPDP11.MEM)) {