Difference between revisions of "PM Opc TST"
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== TST = Test Bits == | == TST = Test Bits == | ||
| − | {| border="1" style="text-align:left" | + | {| border="1" style="text-align:left" class="sortable" |
!Hex | !Hex | ||
!Mnemonic | !Mnemonic | ||
| Line 40: | Line 40: | ||
; Sc = Source | ; Sc = Source | ||
| − | (discarded) = Sc2 | + | (discarded) = Sc2 AND Sc |
=== Description === | === Description === | ||
| − | "8-Bits Source 2" Logic AND with "8-Bits Source" | + | "8-Bits Source 2" Logic AND with "8-Bits Source", result is discarded. |
Source is usually a mask, Flag Z (Zero) return true if the result masked bits are all 0. | Source is usually a mask, Flag Z (Zero) return true if the result masked bits are all 0. | ||
| Line 66: | Line 66: | ||
Zero: Set when result is 0 | Zero: Set when result is 0 | ||
| − | Sign: Set when | + | Sign: Set when bit 7 of the result is 1 |
| + | |||
| + | Carry and Overflow remain unchanged | ||
=== Examples === | === Examples === | ||
; A = 0x85 | ; A = 0x85 | ||
| − | TST A, $80 | + | '''TST A, $80''' |
; F = (Zero=0):(Sign=1) | ; F = (Zero=0):(Sign=1) | ||
; B = 0xF0 | ; B = 0xF0 | ||
| − | TST B, $04 | + | '''TST B, $04''' |
| − | ; F = (Zero=1):(Sign= | + | ; F = (Zero=1):(Sign=0) |
; A = 0x05 | ; A = 0x05 | ||
| − | TST A, $01 | + | '''TST A, $01''' |
; F = (Zero=0):(Sign=0) | ; F = (Zero=0):(Sign=0) | ||
JNZ OddAccu ; Called when first bit is 1. | JNZ OddAccu ; Called when first bit is 1. | ||
Latest revision as of 00:25, 21 April 2009
TST = Test Bits
| Hex | Mnemonic | Cycles |
|---|---|---|
| 94 | TST A, B | 8 |
| 95 nn | TST [HL], #nn | 12 |
| 96 nn | TST A, #nn | 8 |
| 97 nn | TST B, #nn | 8 |
| DC nn nn | TST [N+#nn], #nn | 16 |
Execute
#nn = Immediate unsigned 8-Bits A = Register A B = Register B [N+#nn] = Memory: (I shl 16) or (N shl 8) or #nn [HL] = Memory: (I shl 16) or HL
; TST Sc2, Sc ; ; Sc2 = Source 2 ; Sc = Source (discarded) = Sc2 AND Sc
Description
"8-Bits Source 2" Logic AND with "8-Bits Source", result is discarded.
Source is usually a mask, Flag Z (Zero) return true if the result masked bits are all 0.
Common usage: Check Bit 0 - Mask $01 Check Bit 1 - Mask $02 Check Bit 2 - Mask $04 Check Bit 3 - Mask $08 Check Bit 4 - Mask $10 Check Bit 5 - Mask $20 Check Bit 6 - Mask $40 Check Bit 7 - Mask $80 Zero result if Bit is 0. Non-zero result if Bit is 1.
Conditions
Zero: Set when result is 0
Sign: Set when bit 7 of the result is 1
Carry and Overflow remain unchanged
Examples
; A = 0x85 TST A, $80 ; F = (Zero=0):(Sign=1)
; B = 0xF0 TST B, $04 ; F = (Zero=1):(Sign=0)
; A = 0x05 TST A, $01 ; F = (Zero=0):(Sign=0) JNZ OddAccu ; Called when first bit is 1. JZ EvenAccu
