TRB: Difference between revisions

Latest revision as of 17:50, 23 August 2024


Basic Info
Addressing Mode	Opcode	Length	Speed
Absolute	1C	3 bytes	6 cycles*
Direct Page	14	2 bytes	5 cycles*


Flags Affected
N	V	M	X	D	I	Z	C
.	.	.	.	.	.	Z	.

TRB (Test and Reset Bits) is a 65c816 instruction that tests and resets bits using the accumulator. For each set bit in the accumulator, TRB clears the corresponding memory bit.

TRB performs a logical AND (conjunction) and the zero flag is set or cleared to reflect whether the conjunction is zero. The conjunction itself is discarded.

Syntax

TRB addr
TRB dp

Cycle Penalties

In both addressing modes, TRB takes two extra cycles if the accumulator is 16 bits wide.
In direct page addressing, TRB takes another extra cycle if the low byte of the direct page register is nonzero.

External Links

Eyes & Lichty, page 513 on TRB
Labiak, page 194 on TRB
snes9x implementation of TRB: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1338
undisbeliever on TRB: https://undisbeliever.net/snesdev/65816-opcodes.html#trb-test-and-reset-memory-bits-against-accumulator]

@@ Line 1: / Line 1: @@
-{| class="wikitable" style="float:right;clear:right;width:30%"
+{| class="wikitable" style="float:right;clear:right;width:40%"
 !colspan="8"|Basic Info
 |+
@@ Line 7: / Line 7: @@
 |'''Speed'''
 |+
-|absolute
+|[[Absolute Addressing | Absolute]]
 |1C
 |3 bytes
-|6 cycles
+|6 cycles*
 |+
-|direct page
+|[[Direct Page Addressing | Direct Page]]
 |14
 |2 bytes
-|5 cycles
+|5 cycles*
 |}
 {| class="wikitable" style="float:right;clear:right;width:30%"
-!colspan="8"|Flags Clobbered
+!colspan="8"|Flags Affected
 |+
-|N
+|[[Negative Flag|N]]
-|V
+|[[Overflow Flag|V]]
-|M
+|[[M Flag|M]]
-|X
+|[[X Flag|X]]
-|D
+|[[Decimal Flag|D]]
-|I
+|[[I Flag|I]]
-|Z
+|[[Zero Flag|Z]]
-|C
+|[[Carry Flag|C]]
 |+
 |.
@@ Line 36: / Line 36: @@
 |.
 |.
-|
+|Z
 |.
 |}
-'''TRB''' (Test and Reset Bits) is a [[65c816]] instruction that tests and resets bits.
+'''TRB''' (Test and Reset Bits) is a [[65c816]] instruction that tests and resets bits using the [[accumulator]].  For each set bit in the accumulator, TRB clears the corresponding memory bit.
+TRB performs a logical AND (conjunction) and the [[zero flag]] is set or cleared to reflect whether the conjunction is zero.  The conjunction itself is discarded.
+==== Syntax ====
+<pre>
+TRB addr
+TRB dp
+</pre>
+==== Cycle Penalties ====
+* In both [[addressing modes]], TRB takes two extra cycles if the accumulator is 16 bits wide.
+* In [[direct page addressing]], TRB takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
 === See Also ===
 * [[TSB]]
+* [[BIT]]
+* [[REP]]
+* [[TCLR1]]
 === External Links ===
-* [[Eyes & Lichty]] page on TRB: https://archive.org/details/0893037893ProgrammingThe65816/page/n539
+* [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/513 page 513] on TRB
-* [[Labiak]] page on TRB: https://archive.org/details/Programming_the_65816/page/n204
+* [[Labiak]], [https://archive.org/details/Programming_the_65816/page/n204 page 194] on TRB
 * snes9x implementation of TRB: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1338
 * undisbeliever on TRB: https://undisbeliever.net/snesdev/65816-opcodes.html#trb-test-and-reset-memory-bits-against-accumulator
@@ Line 53: / Line 68: @@
 [[Category:ASM]]
 [[Category:Read-Modify-Write Instructions]]
+[[Category:Test-and-Change-Bits Instructions]]]
 [[Category:65c02 additions]]