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Updated comments in readSrcWord()

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Jeff 2016-11-13 11:50:07 -08:00 • committed by Jeff Parsons
commit 85163fe823
1 changed files with 11 additions and 10 deletions
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21
modules/pdp11/lib/cpustate.js
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@ -2056,8 +2056,8 @@ CPUStatePDP11.prototype.writeWordToPrevSpace = function(opCode, accessFlags, dat
*
* WARNING: If the SRC operand is a register, we return a negative register number rather than the
* register value, because the final value of the register must be resolved AFTER the DST operand has
* been decoded and any pre-decrement or post-increment operations have been performed. See readSrcWord()
* for more details.
* been decoded and any pre-decrement or post-increment operations affecting the SRC register have
* been completed. See readSrcWord() for more details.
*
* @this {CPUStatePDP11}
* @param {number} opCode
@ -2082,7 +2082,8 @@ CPUStatePDP11.prototype.readSrcByte = function(opCode)
*
* WARNING: If the SRC operand is a register, we return a negative register number rather than the
* register value, because the final value of the register must be resolved AFTER the DST operand has
* been decoded and any pre-decrement or post-increment operations have been performed.
* been decoded and any pre-decrement or post-increment operations affecting the SRC register have
* been completed.
*
* Here's an example from DEC's "TRAP TEST":
*
@ -2092,12 +2093,12 @@ CPUStatePDP11.prototype.readSrcByte = function(opCode)
* 007214: 001401 BEQ 007220
* 007216: 000000 HALT
*
* If we returned the value of R0 immediately, then "MOV R0,(R0)+" would write 6340 to the memory location,
* rather than 6342.
* If this function returned the value of R0 for the SRC operand of "MOV R0,(R0)+", then the operation
* would write 6340 to the destination, rather than 6342.
*
* Most callers don't need to worry about this, because if they pass the result from readSrcWord() directly
* to writeDstWord() or updateDstWord(), those functions will take care of converting any negative register
* number back into the proper register value. The exceptions are opcodes that don't modify the DST operand
* number back into the current register value. The exceptions are opcodes that don't modify the DST operand
* (BIT, BITB, CMP, and CMPB); those opcode handlers must deal with negative register numbers themselves.
*
* @this {CPUStatePDP11}
@ -2175,7 +2176,7 @@ CPUStatePDP11.prototype.readDstWord = function(opCode)
/**
* updateDstByte(opCode, data, fnOp)
*
* Used whenever the dst operand (as described by opCode) needs to be read before writing.
* Used whenever the DST operand (as described by opCode) needs to be read before writing.
*
* @this {CPUStatePDP11}
* @param {number} opCode
@ -2200,7 +2201,7 @@ CPUStatePDP11.prototype.updateDstByte = function(opCode, data, fnOp)
/**
* updateDstWord(opCode, data, fnOp)
*
* Used whenever the dst operand (as described by opCode) needs to be read before writing.
* Used whenever the DST operand (as described by opCode) needs to be read before writing.
*
* @this {CPUStatePDP11}
* @param {number} opCode
@ -2229,7 +2230,7 @@ CPUStatePDP11.prototype.updateDstWord = function(opCode, data, fnOp)
/**
* writeDstByte(opCode, data, writeFlags)
*
* Used whenever the dst operand (as described by opCode) does NOT need to be read before writing.
* Used whenever the DST operand (as described by opCode) does NOT need to be read before writing.
*
* @this {CPUStatePDP11}
* @param {number} opCode
@ -2266,7 +2267,7 @@ CPUStatePDP11.prototype.writeDstByte = function(opCode, data, writeFlags)
/**
* writeDstWord(opCode, data)
*
* Used whenever the dst operand (as described by opCode) does NOT need to be read before writing.
* Used whenever the DST operand (as described by opCode) does NOT need to be read before writing.
*
* @this {CPUStatePDP11}
* @param {number} opCode