From f9e3b57a796a03cd8f53b09cb95a19f671583f6d Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Thu, 17 Oct 2019 17:41:50 +0200
Subject: [PATCH] small keyboard reading fixes

---
 STATUS.md                                 |   2 +-
 bin/basic_generic.rom                     | Bin 8192 -> 8192 bytes
 bin/basic_mega65.rom                      | Bin 8192 -> 8192 bytes
 bin/basic_ultimate64.rom                  | Bin 8192 -> 8192 bytes
 bin/kernal_generic.rom                    | Bin 8192 -> 8192 bytes
 bin/kernal_mega65.rom                     | Bin 8192 -> 8192 bytes
 bin/kernal_ultimate64.rom                 | Bin 8192 -> 8192 bytes
 c64/kernal/f13e.getin.s                   |  21 ++-------------
 c64/kernal/interrupts/udtim.s             |  12 ++++++---
 c64/kernal/keyboard/f142.interop          |   4 +++
 c64/kernal/keyboard/f142.read_kb_buf.s    |  30 ++++++++++++++++++++++
 c64/kernal/keyboard/keyboard_disconnect.s |   7 +++++
 c64/kernal/keyboard/pop_keyboard_buffer.s |   4 ++-
 c64/kernal/keyboard/scnkey.s              |   3 +--
 14 files changed, 57 insertions(+), 26 deletions(-)
 create mode 100644 c64/kernal/keyboard/f142.interop
 create mode 100644 c64/kernal/keyboard/f142.read_kb_buf.s

diff --git a/STATUS.md b/STATUS.md
index 40464b97..28523aaa 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -134,7 +134,7 @@ NOTE: Even the 'DONE' routines won't support features described as missing in on
 | `$FFDB`   |            | `SETTIM`    | DONE     |                                                      |
 | `$FFDE`   |            | `RDTIM`     | DONE     |                                                      |
 | `$FFE1`   | `$F6ED`    | `STOP`      | DONE     |                                                      |
-| `$FFE4`   | `$F13E`    | `GETIN`     | PARTIAL  | only some devices supported                          |
+| `$FFE4`   | `$F13E`    | `GETIN`     | PARTIAL  | only keyaboard supported                             |
 | `$FFE7`   | `$F32F`    | `CLALL`     | DONE     |                                                      |
 | `$FFEA`   |            | `UDTIM`     | DONE     |                                                      |
 | `$FFED`   |            | `SCREEN`    | DONE     |                                                      |
diff --git a/bin/basic_generic.rom b/bin/basic_generic.rom
index 40b293f5d165bc4b9809cd782ebedb3a55b640f0..89242f1bdb61bb7ddb0cf07bdcbc760735d8dc70 100644
GIT binary patch
delta 26
icmZp0XmHrDij7U{=h6)dTAMepr86?-ZkFJ9Ar1hGUkSPZ

delta 26
icmZp0XmHrDij7VA=h6)d%9}T^r86?7ZI<A8Ar1hFTnVKB

diff --git a/bin/basic_mega65.rom b/bin/basic_mega65.rom
index d74a3c0a02752a819872cd65de74c4a6ef2c3f41..5fff525b5bb132a45f4e935c947cead277d5282b 100644
GIT binary patch
delta 20
ccmZp0XmHrDpN+lx-_i{V)&DjhW3!S30Ab4sHUIzs

delta 20
ccmZp0XmHrDpN;+KkEI(Fj{ewujLk|C0A}L}z5oCK

diff --git a/bin/basic_ultimate64.rom b/bin/basic_ultimate64.rom
index b63c2cb9984aed6f4be91faf7dd8033fe4fc3c59..36620ad7c6b9019177b0172ea8e3424ba289d74a 100644
GIT binary patch
delta 14
VcmZp0XmHrT%g)%enUDRG1OOv;1eyQ<

delta 14
VcmZp0XmHrT%g$K6nUDRG1OOvU1d{*&

diff --git a/bin/kernal_generic.rom b/bin/kernal_generic.rom
index 4c60712cae5fad39fd78c1b73973a5e34cadf9db..15295fdd254e3033fb43e329a0f710b8c408c001 100644
GIT binary patch
delta 1026
zcmXYwZ)lrE9LJw~(&R}p(<W`&KK*}Pr)y$o6Q|IDur`W>dTd}{tSV!V9Y_ZCMMba`
zhI`Q`jCPgPQ<#I&^r6pa<_eibx5rtj^UqB8=3$5|<?&6|6gnn6ZEWtIYJ9v@;kY~Q
zclW#det)04(0idbV^lo1nbKXGb9(irlD4P1_4G$moUsTDd0JBEvW@y<Rmq;zH`1J}
z$aAKFz0ME8F)TZe9+Yp5f1A7`O~kLn-J@`fD)u7xd)P0m>ZB7@Se<AOuQ|^)<w(M;
zk1KqNhfn1baTvA|S)e<W*I*70x_ZDfc-j>`>>^Mja9~FX>?f&WNnm>c-Xrk+e^^8j
z(p((62;Opa1n-fAJfB!dTvzACK}r4G3_ygT5CZpczt9WrFHH(JfLLuYA)070O<JpU
z1Q@z!af)v^gim_HjS=#MEyUHLc|2vqYnCD`pV?;nmn$*$ghKmavm<TGKS|7sP*uv2
z1Jtaz=%<qAq4KWgqjFJmQk?f3<auk!<9$(RK(TF3{aNRGq{R<-<_c^nu~&)`hff8@
z0m4S$YcWbQG3_i55y><|F|WPLXC>VQXYuvwBv{AMn%CWkT;@dy2JmFf`4_&TXm^{X
zsw_-EcJ_I8HVe#1mN&b!H_Fo^|7Y{TKAI8P8l1*21-n2Lp9?lsvTJ-WKr?sC0U3W1
zd=>=ocflsmhu4Cq!7T2n?eET!6!+sT({u9<d|>~AlDm>R<Nr&kQnAS^^)N@2PS&Y+
zS?Sd8Q5fH>jd|@N93s#zqP?Y3Ee`~r?O;v9cHIcb;gR|dR@cw!#||(t4piLnKy(5(
zh)**Yj*D+O+vx<;H!JqnZP3I5JX%1N1xDDX<)Sj_L)aGI!;H<BFL8##mrK*FFTZK|
zfRVM$rWIRnO9{C%+xmek;`z0mbG-}bH|wJRkBEEK|6s*7IVq7qKWtrlXgW{~uQwo2
zx76KugBKnu_SI21gSVPt4a1E=_XT5hkBX_15<#bNb4%=%OLUZRc-aL9N^FFu$^<Hc
zI^QqPXIu<OG+rvB$_!v3ySVD#7~Ch{?_Sku#KFjC;43XL_Yje9k88<q@ROFe!3;jp
z8m)SV!ea#nxWBv&YWU;UM(-m_{nh#3OTTQz>~Fo=2AORc2W+S6RYvwmTSu2n&@@3i
z1U(`sw1wvWL{<?^=21IEvBxMtQ6EKP1Z|ek?L1y-Yd&<CpjI;6=@<?>hPxcd*g(lV
S^5#>9!bu!AK-d2swf+T=AlLN(

delta 1020
zcmXX_Z)jUp6wiHW@|w&nsZGgC+O*e3v5B2+=O1bvT8f>aUfi&tl_GtzFBw#@MX(C{
z^P#Vd*2?CA5yyn|kyo0rO4fpFoRv81F#Yt1V{G*eL6%B&;%j4bU!2+VrU;jNFXwm8
zx%Zs&`<?DR-J8~GV8Z`2IBg%JgCN<SX?2-aw#4aZJX$+}#|_zBwA_t&_;r=Gk&4kq
zim+ij)|jU;-4~U)1cx6f#G*J<j^&VQlV8Jm7_xVx7C2|`deSW6C5i`k<hs2iZk7Z;
zR>WC~KX}LxnNL}w*et=8J><>On3Rky#4agGVMtUy*XwXUU_Ol2V1VyMYs)kIWhCq?
z&swxhU3s=c&G^a(kfu5oXE}cmjyNKLFul(VQKh86oG|glvdpiJY%~8=9>5U}@4<Q~
zWlBGYi%1K*6V^NbP`&1i#}G4|A?;@DhE&Qtq)>3Qau1AUhx0k!uiQ{;x>FW$@k1_(
zgO!*dN-L9@sjo$Nt8NnYgI4#I5HZqynPVL8r|Bjv6f*B|IZ?IaI9z&k3jGXS^>5Vn
z)3cl)VkgYhpLq65gY0g{qj-OD8nf7gEH;Pq&K#$=XWp(}5B#6ag?o&&z-)LL4td*A
z1de+f_p@hQ*lDD%SAmo8nfEE=gm1l#s0TK@@1QtzHw<*-X~MF0Rd-yuhV$l+WNKGb
zzVJMd-3sWO?8A8~x3NvR&PJzvM?!F=q0hNez{3=;6i9Ko(!e3G`^HcnCVU|_&x^i~
z_OT+Yq_pF}<W<1J6Ri5f!mur1OtZS?g#mOIwgoR52D^X!)Mi4pZ_cUiO*wUn&44vr
zI!D4(nac&#KNUH5MExygkz{F3|K$^lCUezMb*QU@Wf#(NrtZ(0YHNbOGqSBZ;=+lI
zodvR9KI8eT)3xronKgBr5I^3#AjV?k`>pxgx|O_0=YLW?$y<8Yja&H8E>QnV$i4i0
z;4%mATY3JrY+jha=V7Y}*E3EsW+oY-i-wS>$erX(XbSedA{i5mtY__bu)<D!v`SN%
zSCRu#GHqw9C6kpZpIMg}v{G32+#A}Hho^R3H9D<K9!wo_u&;KQN>?YpnYsq|gYTmA
z@OpEXd&Iym6qyP<RX4l@pEd`aT3NYi+xt5#H3Jji;TFt#oVMbCp<H0}A8QG<pQL1(
zl0PWXC<$+oxxY!dL}m&kV35AwiPIoG1{tU1=r-A`K(?jnaZHJij<#7xBi7M&D;X=3
UsRD5p5}IrgEf!+@`mc8HKjzulD*ylh

diff --git a/bin/kernal_mega65.rom b/bin/kernal_mega65.rom
index e7c74f77d2fbc07908b10ef52ebd02f43ee8cbc2..c8395834882e1e7c24e5065c4648f4f930c70c88 100644
GIT binary patch
delta 805
zcmYjNUr19?7{B+<UFWXmHeKG0jU592R$v4%eNiH5vlBjys0j4-68g}K1xXV6;FVAm
z^-%O8=<rGl2Eq`tdeBJYYT&_%X=rKb#E6{Baktj4oht^Nm+$xczVrRQ@B6h^w^xsO
z*v$DPIFkSip*r@Pj`pMTMlWp$Ju*(SCGg@tCCy^SEd(Dho@XBNukm>!FHkTe5}?En
z0w_`fRnUd*n44({t(woWGl?-BOrmUyjpk61r6h+-!J&ANS~sNxP=jt+ZZI<mG;S%>
z4;deu(&&q2oVKDTd9_TdiZ=7QGh0<@8WMaj|2iqm=R3=15`8*2Z~&6WaVJT*Q5~I(
zGU7D&pS=aw4!{oLt;N}(NQFB|aiZf*=WBGu`jjivx-4qe26TmfSlu+ehzbkbv<uZ2
zjA|>f{7o&~=1&q2TKKEBF70480V;lJ+w0&&0<<bT6w+v&cYFWIMa2<tbn})X$fiD4
z7NW#1UWg1~HZqKJBK|;I549Gg*TjB78kX&NPx8xkc$fI+7l)&pNU+&x1A1sHCWiTK
zK5NWxCIib%xpP<n6)L!^fKM@Gw0pV1-y_SDtCUFx22s7;Yg<T4A77LTSO<~XC2x#n
z$y0s$(l)plnzEl_(59o3{)`;XN=JE0IJ(A}ZUMen9}9eG62Uo5In?ZA=r-|X$7JU#
zA>pYdPc}A{gT=$f(p(L#z{SHZIR|rO<0WxLd=G2C%lTwzLsDAOuS9jwp>)ap*eHeF
zyCq^68d9<u=SX3`i7?O|(Gr80la}@2C^LIhcVd0y2v~4NpdGV<Jb*Ka{(H!!<X+4L
zd0fi$@K~cKa3-Ny4BqqSuD??-+uO;I{G2H!XJJEt>gm_0Y#_M(80TRY(2ABt1YO#O
z9P+t*_NqAS-iGQvY}kiC<M2R%mlb$lg*9<B<vMM>kc8$KG;R;A`6+>-Y>BUb*0%lv
D7};;G

delta 806
zcmYjNTSyd97@nDRNB3fT(aqV#)kENAyMPhF+KWDPS@nd$5*1NSFQE^;SdbZ^4~~SQ
zsE4ALL^ns+KoAx&D@Y@iF&_@Dn8uoBx><BtO_|xY9Xn$MotN+X{{KJU`Onu_+E_a1
zV^gQ&;GhC<sFMAlqaUFo#xmLvx?>z;3&jbX;tf*#z)i+SW~w<}7;bvr{EUYw(I6#E
z^B`XimcSfz)mBUQqXpX`wq707K?RxZPTGv}?S<*)1nk)k?6gx69-KrM?dO?#6%E<*
z^aIplQ35U5hv-anFQc3pSJ3;6*3@xD9D{^k&pbyOuQT06^=gL>c5MMg`Gf0mf=0D}
zB*qA1;D7ZJoZSNJh;tN}dyIFjNnUu;G}8PORXFaOJlZY0YFLIjp)U?EO@~olmY2>!
zm$Uk{m00eA23NSfB!fEcG^hB=$&rjTMPO#9+GEk!Je=7<?>KM8Kew3B2X?=_D)W-H
zgO&Ig<K;O%+Jo6>FSbMj!G<;}GC)U!PUznhdnFhCDh8xV{E-A05PD-vsLJW24d|A$
zfF#!I^gEIP8_8zB)iQ-;P^^M$GAP+b23MJ>`)A+W$O2{6fo^okRp!KT@y%lok982K
zEz<I!K^pDQdm3Ok^uo1|K`YtC^dic3AIr8T_!i#-A8;q@fIr#6g14Il!C}ogRO@Ew
z29U49_4w`(tAOGkWCN=X4lCfc%t1ccBBf&!*?3l%7bao(XDO3B%E!f7{d`OZv*i}4
z6C1^__fw$|hK7V>!|7s}t04-sMzz92Y!c`6;TSWq+jnDqbeGt1O0W^LywrtLiT@-t
zC!}_48sM;pY2&aa_uy0_4GjJsuq?ikG27nEkouH$Q!?PRAl25XNhyu+#=krRvw)Vh
zDkALo8Z;w+uHSV-g{^B)-GEga@Y^=rlHn;Cp4f(GHqdD90msoev~5D;T2CZE@f77$
JR(?fRe*@gna6141

diff --git a/bin/kernal_ultimate64.rom b/bin/kernal_ultimate64.rom
index 5caf1cfbdfb24c0039720f63414d9c1a5735d4b9..a69028efb8ddb5df81d702bc5663be9c9c757955 100644
GIT binary patch
delta 932
zcmX9-ZD<@t7~a`!Zgba<?4_67rfHH_8jrIknpzNB8wuAMj&`hIO^knZv42i-{!siV
z6*R(aY!jNMP77^{aJSrsUNCUYN!znU+9Kjb4679Bj}>ZZf(>%6#$@Ku%{hDinRl4y
zosZ{ZM*2qj@(YqrshD|C3U{PDLNTJ(^=@3Cpi;O=qnME&>fS=%lV^S75x&HMBd!sg
z6@J;NG|XER9$5jK!Uhj9<eU%(mHh7O4B0fHXA_qaGiFvD(##7^5C%x6{1_^c!*U-g
z6;8`vpvL#<DZwrtr`^c5{IjRTmXF8_{$2!R+}|5|nmHRzC`>Cp$Mn@=jOlB|y#?F<
zhTMW<e+uTemiUY|`+*ogABQ%VU!`gSc_o-a1H=wq@%OWQtaw!9w_a>KhwhPGTVJXl
zpp&AiL4=HNJsIT<Pw|Ela(YUl(^Y)cn|9Z>(EMf?WO<dZ!8F+y>O%eG%~0!>0S}0<
z{A~}IBA<mGM-lRMsI_U3O-lI3)tshh;rM!O4*N+tboR+IO$*;#b^MpF!%x-k@aU>$
zey;puG?>H@jWCp{5#@t<8@LCzutF|3JueSa2vE!lZc_;P^sA{Gqt}TNeh-z&Xm|%|
zB{Si78uwQ;P#1wSlJMGJe!xe`6Y8U!`^#z)-5|HrNb`M`xCFab@RpUFpr7@;;M|9a
ztM(t5U`DlOq0B9eVzI(~W=m<yx0JCqFB!Ryxh=EE*3W2WrnJra!!$}SS`Ya#hMsYL
zoxbZx_z*eSf>E^abBiqPy=zpbj=>zYq@*wcsVaP0g|RApQXNVP=^1EdV_de}y_z~u
zUWM4Qrlwt^2S>^Fw%CCTJH}Hr>4SIIc?HeOlOdbggL*da<MF~N*9%^NdQgDQD-VWh
z?^o*QE!HFP_w$$<ZAa>dseUb09Q}&8ZSA|uG~tBfhL{#%(_$jd6;70pRc9RXR2L?|
z`b}{SAFs=n6Cd+pG)E4%?`rsv!JZYaj^Z5*3uK~wTi`^+yi@l-?YVZsKS_TFY~*o}
zI5%^OhwSZ+9bHotPg5*2%qZ@Dh%<lV^)>t@!_5rGmT`pPL53$NrY;Ura<gN5XAi}D
gXfi4#cS^}F3BO*!uT^niF>M=yCI|_3|6lvTf0@0i6aWAK

delta 931
zcmX9-ZD?Cn7``XB$?eT_NxEBev#rfrR!25l)~$#iZCNR^1U;r=f7qeORr@1C#IM4J
zf2^3>YD;VNOwfufz2uH%GmtLK87HDewxyt4WrN8gimZ(m9k;9PIc28t-1z6bhx5GW
z<M}wFy`#OkA4HG5Y34xAUlnr*brId&v+Xj40EGgL;8pUy`z3UVba^KC@+A%oR*XPa
z_+`J}w`fslS%Yg7>Kw$7GC~vr<S$RFa*f9Ibo_MujG0!4H1lIS05Q@k?L!MBCiS9)
z{Cm=8sNrQgC6o%U({@y{<m{9ybc{SM_n;7&lzWr|%&vRK&$Pk=OkXc_F@2-ZnJ>xD
zOCj@;Rrg><(6Yx|QD~~fRZagQSs43LBTogAC`L+w&*j4`*H?JK#c%zj;Y0K@Ik@A=
z`WT&YsTzdI<c@bEyx|aUC?dO~=(5`iN1bVVZ41ra4FfEv@-;X~x|KF`n7pX$+8%R&
zFv~4C03jbJ_n|QPTG`b&z-C1J<9bHZ)9}VtZ4TY!mU7}inWlvAF4*$?Mfj<D1&^(3
z=BNHUhR-Cn%Lqc58WBF23&1`27RzM5@eyg5f|ugee5FxAL=BFhGMNhQK?<1<zShva
zse!r#oQjAyZp(n5A@{5Ia?($$33Q%ZQTN_+gT+rn=NjI=mJ#$5jtQLfFsTdm_m4B9
zTJuig-bL^o#tml6Da*4wXZe<m%$wYgEGp^m<H6hJTydxMw`mjytTI2y(C6%5PhGb~
ze1uGgFlx!)2uUJ&MRY%W-KfqUhqKfY6T&DYt1w=Li7LER9ZCqPGvH$rT(!(^HF4n9
zI`pk*YN}#%;1;sGsqe@vJI+Hj<AISaUg4+{CqpvRkLu~1ho=iCD^Bjb)PcNo(SLKO
z#=>8}Xt55Fv*0N;ng;8KseU2()!0Q+X=?5))3_as8m^QJ?plgRxxn!vvfRdFj_ATP
zSbz8{hKJV`%Z^S&KZ?Rx5^Fx_8)5L!8rR7091NGqbn{N{+neT9_y5$-H52|v`opk|
zr$OZ0%vqkXSHpYS2*oEU7WiW*ZvPX{{e!nQaF$^o!+k3_%<uri;}k!!ifM&>6W-mr
kkK#i#5fKyn#YCHkhc@xERqS0#l?*`>gy-1r|CVn42c}i2mjD0&

diff --git a/c64/kernal/f13e.getin.s b/c64/kernal/f13e.getin.s
index 5eefc0ac..be8e3faa 100644
--- a/c64/kernal/f13e.getin.s
+++ b/c64/kernal/f13e.getin.s
@@ -8,26 +8,9 @@
 // CPU registers that has to be preserved (see [RG64]): .X, .Y
 //
 
-// XXX currently does not preserve registers, to be fixed!
 
 GETIN:
 
-	// Wait for a key
-	lda NDX
-	bne !+
+	// XXX this should be a dispatcher for several different devices!
 
-	// Nothing in keyboard buffer to read
-	sec
-	lda #$00
-	rts
-	
-!:
-	lda KEYD
-	pha
-
-	jsr pop_keyboard_buffer
-
-	pla
-	clc
-
-	rts
+	jmp read_kb_buf
diff --git a/c64/kernal/interrupts/udtim.s b/c64/kernal/interrupts/udtim.s
index 34528613..f9d4fa99 100644
--- a/c64/kernal/interrupts/udtim.s
+++ b/c64/kernal/interrupts/udtim.s
@@ -26,16 +26,22 @@ udtim_update_stkey: // entry to be used when interrupts are disabled
 	// Another action we have to perform is to copy the last row of keyboard to RAM,
 	// so that various routines can detect the STOP key press
 
+#if CONFIG_KEYBOARD_C128
+	lda #$FF
+	sta VIC_XSCAN // disconnect the extra C128 keys
+#endif
+
 	lda #$7F
 	sta CIA1_PRA  // select the last row (bit to 0)
 
 	lda CIA1_PRB  // read the row
 	sta STKEY
 
-	// Finish by disconnecting the keyboard, this will prevent
-	// interference when scanning joystick in port 1
+	// Leave the CIA configured this way. It would be far better to disconnect
+	// the keyboard at this point, but certain software (mainly intros) is
+	// unable to, for example, read the space bar status.
 
-	jmp keyboard_disconnect
+	rts
 
 udtim_clock_rollover:
 
diff --git a/c64/kernal/keyboard/f142.interop b/c64/kernal/keyboard/f142.interop
new file mode 100644
index 00000000..73019c17
--- /dev/null
+++ b/c64/kernal/keyboard/f142.interop
@@ -0,0 +1,4 @@
+$F142 is a well-known address of keyboard reading routine, described for example here:
+- http://sta.c64.org/cbm64kbdfunc.html
+
+It is used for eexample by a music eeditor here: https://github.com/martinpiper/C64Public/blob/master/MusicEditor/GetKey.a
diff --git a/c64/kernal/keyboard/f142.read_kb_buf.s b/c64/kernal/keyboard/f142.read_kb_buf.s
new file mode 100644
index 00000000..8b72b9e2
--- /dev/null
+++ b/c64/kernal/keyboard/f142.read_kb_buf.s
@@ -0,0 +1,30 @@
+
+//
+// Well-known Kernal routine, described in:
+//
+// - http://sta.c64.org/cbm64kbdfunc.html
+//
+
+
+read_kb_buf:
+
+	// Check for a key
+	lda NDX
+	bne !+
+
+	// Nothing in keyboard buffer to read
+	sec
+	rts
+	
+!:
+	lda KEYD
+	pha
+	phy_trash_a
+
+	jsr pop_keyboard_buffer
+
+	ply_trash_a
+	pla
+	clc
+
+	rts
diff --git a/c64/kernal/keyboard/keyboard_disconnect.s b/c64/kernal/keyboard/keyboard_disconnect.s
index 37f4e973..1fdae023 100644
--- a/c64/kernal/keyboard/keyboard_disconnect.s
+++ b/c64/kernal/keyboard/keyboard_disconnect.s
@@ -2,6 +2,10 @@
 //
 // Helper routine - disconnects the keyboard from CIA1_PRB,
 // leaves $FF in .X (behavior needed in some places)
+//
+
+
+#if !CONFIG_LEGACY_SCNKEY
 
 
 keyboard_disconnect:
@@ -13,3 +17,6 @@ keyboard_disconnect:
 #endif
 
 	rts
+
+
+#endif
diff --git a/c64/kernal/keyboard/pop_keyboard_buffer.s b/c64/kernal/keyboard/pop_keyboard_buffer.s
index e540a221..6f3b172b 100644
--- a/c64/kernal/keyboard/pop_keyboard_buffer.s
+++ b/c64/kernal/keyboard/pop_keyboard_buffer.s
@@ -2,7 +2,9 @@
 // Pop key out of keyboard buffer
 // Disable interrupts while reading from keyboard buffer
 // so that no race conditions can occur
-
+//
+// CPU registers that has to be preserved: .X
+//
 
 pop_keyboard_buffer:
 
diff --git a/c64/kernal/keyboard/scnkey.s b/c64/kernal/keyboard/scnkey.s
index a3fb99c5..e35baaf2 100644
--- a/c64/kernal/keyboard/scnkey.s
+++ b/c64/kernal/keyboard/scnkey.s
@@ -53,7 +53,6 @@ SCNKEY:
 #endif
 
 	// Retrieve SHIFT / VENDOR / CTRL status
-	// Use .X to detect 2 or more keys pressed (should be $FF now)
 
 	ldy #(__kb_matrix_bucky_confmask_end - kb_matrix_bucky_confmask - 1)
 scnkey_bucky_loop:
@@ -154,7 +153,7 @@ scnkey_matrix_loop_inner:
 !:
 	dey
 	bpl scnkey_matrix_loop_inner
-	bmi scnkey_no_keys            // branch always, multiple keys must have been pressed
+	bmi scnkey_no_keys             // branch always, multiple keys must have been pressed
 scnkey_matrix_loop_next:
 	dex
 	bpl scnkey_matrix_loop