NOTICE: list the Arnitech controller option

A new option, ARNITECH_CONTROLLER, on in the mc64 configuration only.
IOINIT starts timer A with CIA #1's TOD on 50 Hz, the mc64's mains, and
if the Arnitech controller's signature "ARNI" is at $DE80, latches its
clock and copies its real time into the TOD, hours first and tenths
last, flipping bit 7 of an hour of 12 first, since the CIA flips it
back when 12 is written. Without the signature the TOD is left alone.

The Arnitech jump table at $FF00: "ARNI", version $01, two entries, and
JMPs from $FF06: $FF06 finds the first Card slot holding a Card of the
type in A (carry clear, the slot in A, its Card window's low byte in
X; carry set if none or no controller), $FF09 sets the TOD as IOINIT
does. $FF48-$FF80 stay clear. The code is in new files under
src/kernal/arnitech; other configurations build as before.

CONFIG.md

@@ -289,6 +289,12 @@ On the most widespread CPUs the D flag is not cleared upon entering interrupts.
 
 Feature needs 2 bytes in KERNAL segmment (for CPUs needing the patch), but at the same time allows optimizations allowing to gain some more bytes. If unsure - enable.
 
+### `ARNITECH_CONTROLLER`
+
+For the mc64 computers of arnitech only, whose expansion port holds the Arnitech controller at `$DE80`. IOINIT puts CIA #1's TOD on 50 Hz and, if the controller's signature `"ARNI"` is at `$DE80`, sets the TOD from the controller's clock. The Arnitech jump table at `$FF00` (`src/kernal/arnitech/ff00.arnitech_jumptable.s`) wraps the controller's registers.
+
+Feature needs about 120 bytes in KERNAL segment, and the page at `$FF00`. Disable on any other machine.
+
 ## Eye candy
 
 ### `COLORS_BRAND`

Makefile

@@ -45,6 +45,7 @@ SRCDIR_KERNAL  = $(SRCDIR_COMMON) \
                  src/kernal \
                  src/kernal/,stubs \
                  src/kernal/assets \
+                 src/kernal/arnitech \
                  src/kernal/board_crt \
                  src/kernal/board_m65 \
                  src/kernal/board_u64 \
@@ -137,6 +138,7 @@ GEN_ZMAC_H     = $(DIR_ZMAC_TMP)/doc.inl
 # List of build directories
 
 DIR_C64        = build/target_c64
+DIR_MC64       = build/target_mc64
 DIR_CUS        = build/target_custom
 DIR_GEN        = build/target_generic
 DIR_GENCRT     = build/target_generic_crt
@@ -151,6 +153,7 @@ DIR_X16        = build/target_cx16
 
 CFG_CUS        = src/,,config_custom.s 
 CFG_C64        = src/,,config_c64.s
+CFG_MC64       = src/,,config_mc64.s
 CFG_GEN        = src/,,config_generic.s
 CFG_GENCRT     = src/,,config_generic_crt.s
 CFG_TST38      = src/,,config_testing_38K.s
@@ -164,6 +167,7 @@ CFG_U64CRT     = src/,,config_ultimate64_crt.s
 
 GEN_STR_CUS    = $(DIR_CUS)/,generated/,packed_strings.s
 GEN_STR_C64    = $(DIR_C64)/,generated/,packed_strings.s
+GEN_STR_MC64   = $(DIR_MC64)/,generated/,packed_strings.s
 GEN_STR_GEN    = $(DIR_GEN)/,generated/,packed_strings.s
 GEN_STR_GENCRT = $(DIR_GENCRT)/,generated/,packed_strings.s
 GEN_STR_TST38  = $(DIR_TST38)/,generated/,packed_strings.s
@@ -212,6 +216,7 @@ TARGET_CHR_PXL     = build/chargen_pxlfont.rom
 
 TARGET_CUS_B       = build/basic_custom.rom
 TARGET_C64_B       = build/basic_c64.rom
+TARGET_MC64_B      = build/basic_mc64.rom
 TARGET_GEN_B       = build/basic_generic.rom
 TARGET_GENCRT_B    = build/basic_generic_crt.rom
 TARGET_TST38_B     = build/basic_testing_38K.rom
@@ -221,6 +226,7 @@ TARGET_U64CRT_B    = build/basic_ultimate64_crt.rom
 
 TARGET_CUS_K       = build/kernal_custom.rom
 TARGET_C64_K       = build/kernal_c64.rom
+TARGET_MC64_K      = build/kernal_mc64.rom
 TARGET_GEN_K       = build/kernal_generic.rom
 TARGET_GENCRT_K    = build/kernal_generic_crt.rom
 TARGET_TST38_K     = build/kernal_testing_38K.rom
@@ -237,6 +243,7 @@ TARGET_X16_x       = build/cx16-dummy.rom
 
 TARGET_LIST_CUS    = $(TARGET_CUS_B) $(TARGET_CUS_K)
 TARGET_LIST_C64    = $(TARGET_C64_B) $(TARGET_C64_K)
+TARGET_LIST_MC64   = $(TARGET_MC64_B) $(TARGET_MC64_K)
 TARGET_LIST_GEN    = $(TARGET_GEN_B) $(TARGET_GEN_K)
 TARGET_LIST_GENCRT = $(TARGET_GENCRT_B) $(TARGET_GENCRT_K) $(TARGET_GENCRT_X)
 TARGET_LIST_TST38  = $(TARGET_TST38_B) $(TARGET_TST38_K)
@@ -249,6 +256,7 @@ TARGET_Z80TEST     = ./build/cpm/Z80TEST.COM
 TARGET_LIST        = $(TARGET_CHR_ORF)     \
                      $(TARGET_LIST_CUS)    \
                      $(TARGET_LIST_C64)    \
+                     $(TARGET_LIST_MC64)   \
                      $(TARGET_LIST_GEN)    \
                      $(TARGET_LIST_GENCRT) \
                      $(TARGET_LIST_TST38)  \
@@ -385,6 +393,8 @@ $(DIR_CUS)/OUTB_x.BIN $(DIR_CUS)/BASIC_combined.vs: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_BASIC) $(CFG_CUS) $(GEN_STR_CUS) $(DIR_CUS)/KERNAL_combined.sym
 $(DIR_C64)/OUTB_x.BIN $(DIR_C64)/BASIC_combined.vs: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_BASIC) $(CFG_C64) $(GEN_STR_C64) $(DIR_C64)/KERNAL_combined.sym
+$(DIR_MC64)/OUTB_x.BIN $(DIR_MC64)/BASIC_combined.vs: \
+    $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_BASIC) $(CFG_MC64) $(GEN_STR_MC64) $(DIR_MC64)/KERNAL_combined.sym
 $(DIR_GEN)/OUTB_x.BIN $(DIR_GEN)/BASIC_combined.vs: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_BASIC) $(CFG_GEN) $(GEN_STR_GEN) $(DIR_GEN)/KERNAL_combined.sym
 $(DIR_TST38)/OUTB_x.BIN $(DIR_TST38)/BASIC_combined.vs: \
@@ -398,6 +408,8 @@ $(DIR_CUS)/OUTK_x.BIN $(DIR_CUS)/KERNAL_combined.vs $(DIR_CUS)/KERNAL_combined.s
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_KERNAL) $(CFG_CUS) $(GEN_STR_CUS)
 $(DIR_C64)/OUTK_x.BIN $(DIR_C64)/KERNAL_combined.vs $(DIR_C64)/KERNAL_combined.sym: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_KERNAL) $(CFG_C64) $(GEN_STR_C64)
+$(DIR_MC64)/OUTK_x.BIN $(DIR_MC64)/KERNAL_combined.vs $(DIR_MC64)/KERNAL_combined.sym: \
+    $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_KERNAL) $(CFG_MC64) $(GEN_STR_MC64)
 $(DIR_GEN)/OUTK_x.BIN $(DIR_GEN)/KERNAL_combined.vs $(DIR_GEN)/KERNAL_combined.sym: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(DEP_KERNAL) $(CFG_GEN) $(GEN_STR_GEN)
 $(DIR_TST38)/OUTK_x.BIN $(DIR_TST38)/KERNAL_combined.vs $(DIR_TST38)/KERNAL_combined.sym: \
@@ -457,6 +469,7 @@ $(DIR_X16)/kernal.seg_1 $(DIR_X16)/KERNAL_1_combined.vs $(DIR_X16)/KERNAL_1_comb
 
 $(DIR_CUS)/OUTx_x.BIN:     $(DIR_CUS)/OUTB_x.BIN     $(DIR_CUS)/OUTK_x.BIN
 $(DIR_C64)/OUTx_x.BIN:     $(DIR_C64)/OUTB_x.BIN     $(DIR_C64)/OUTK_x.BIN
+$(DIR_MC64)/OUTx_x.BIN:    $(DIR_MC64)/OUTB_x.BIN    $(DIR_MC64)/OUTK_x.BIN
 $(DIR_GEN)/OUTx_x.BIN:     $(DIR_GEN)/OUTB_x.BIN     $(DIR_GEN)/OUTK_x.BIN
 $(DIR_GENCRT)/OUTx_0.BIN:  $(DIR_GENCRT)/OUTB_0.BIN  $(DIR_GENCRT)/OUTK_0.BIN
 $(DIR_TST38)/OUTx_x.BIN:   $(DIR_TST38)/OUTB_x.BIN   $(DIR_TST38)/OUTK_x.BIN
@@ -468,6 +481,7 @@ $(DIR_X16)/OUTx_0.BIN:     $(DIR_X16)/OUTB_0.BIN     $(DIR_X16)/OUTK_0.BIN
 
 $(TARGET_CUS_B):    $(DIR_CUS)/OUTx_x.BIN
 $(TARGET_C64_B):    $(DIR_C64)/OUTx_x.BIN
+$(TARGET_MC64_B):   $(DIR_MC64)/OUTx_x.BIN
 $(TARGET_GEN_B):    $(DIR_GEN)/OUTx_x.BIN
 $(TARGET_TST38_B):  $(DIR_TST38)/OUTx_x.BIN
 $(TARGET_TST60_B):  $(DIR_TST60)/OUTx_x.BIN
@@ -475,6 +489,7 @@ $(TARGET_U64_B):    $(DIR_U64)/OUTx_x.BIN
 
 $(TARGET_CUS_K):    $(DIR_CUS)/OUTx_x.BIN
 $(TARGET_C64_K):    $(DIR_C64)/OUTx_x.BIN
+$(TARGET_MC64_K):   $(DIR_MC64)/OUTx_x.BIN
 $(TARGET_GEN_K):    $(DIR_GEN)/OUTx_x.BIN
 $(TARGET_TST38_K):  $(DIR_TST38)/OUTx_x.BIN
 $(TARGET_TST60_K):  $(DIR_TST60)/OUTx_x.BIN
@@ -482,6 +497,7 @@ $(TARGET_U64_K):    $(DIR_U64)/OUTx_x.BIN
 
 build/symbols_custom.vs:          $(DIR_CUS)/BASIC_combined.vs       $(DIR_CUS)/KERNAL_combined.vs
 build/symbols_c64.vs:             $(DIR_C64)/BASIC_combined.vs       $(DIR_C64)/KERNAL_combined.vs
+build/symbols_mc64.vs:            $(DIR_MC64)/BASIC_combined.vs      $(DIR_MC64)/KERNAL_combined.vs
 build/symbols_generic.vs:         $(DIR_GEN)/BASIC_combined.vs       $(DIR_GEN)/KERNAL_combined.vs
 build/symbols_generic_crt.vs:     $(DIR_GENCRT)/BASIC_0_combined.vs  $(DIR_GENCRT)/KERNAL_0_combined.vs
 build/symbols_testing_38K.vs:     $(DIR_TST38)/BASIC_combined.vs     $(DIR_TST38)/KERNAL_combined.vs
@@ -499,6 +515,10 @@ $(GEN_STR_C64): $(TOOL_GENERATE_STRINGS) $(CFG_C64)
 	@mkdir -p $(DIR_C64)/,generated
 	$(TOOL_GENERATE_STRINGS) -o $@ -c $(CFG_C64)
 
+$(GEN_STR_MC64): $(TOOL_GENERATE_STRINGS) $(CFG_MC64)
+	@mkdir -p $(DIR_MC64)/,generated
+	$(TOOL_GENERATE_STRINGS) -o $@ -c $(CFG_MC64)
+
 $(GEN_STR_GEN): $(TOOL_GENERATE_STRINGS) $(CFG_GEN)
 	@mkdir -p $(DIR_GEN)/,generated
 	$(TOOL_GENERATE_STRINGS) -o $@ -c $(CFG_GEN)
@@ -541,6 +561,7 @@ build/,generated/,z80_tables.s: $(TOOL_GENERATE_Z80_TABLES)
 
 GEN_STR_custom         = $(GEN_STR_CUS)
 GEN_STR_c64            = $(GEN_STR_C64)
+GEN_STR_mc64           = $(GEN_STR_MC64)
 GEN_STR_generic        = $(GEN_STR_GEN)
 GEN_STR_generic_crt    = $(GEN_STR_GENCRT)
 GEN_STR_testing_38K    = $(GEN_STR_TST38)

NOTICE

@@ -0,0 +1,39 @@
+This is a modified version of MEGA65 Open ROMs (https://github.com/MEGA65/open-roms),
+forked at upstream commit ad178dbe4d48cd6a317737a8e0e7e662f7e33d32.
+
+Modified by Christian Werner, 2026-10-14, 2026-10-15, and 2026-10-17, for the mc64
+computers of arnitech, a set of Minecraft mods (https://git.susdog.de/chris/arnitech). The
+fork lives at https://git.susdog.de/chris/open-roms, branch mc64.
+
+Changes:
+
+- src/,,config_mc64.s: a new build configuration, copied from src/,,config_c64.s, with its
+  own config ID ($6D), the brand "MC64", and BCD_SAFE_INTERRUPTS turned off.
+- Makefile: targets for that configuration, build/kernal_mc64.rom and build/basic_mc64.rom,
+  made the same way as the c64 ones.
+- src/kernal/iec/ciout.s (2026-10-15): CIOUT buffers its byte in TBTCNT, where the send
+  routine takes it from, not in BSOUR (upstream PR #113).
+- src/kernal/iec/close_iec.s (2026-10-15): CLOSE sends LISTEN, $E0 plus the secondary
+  address, and UNLISTEN; it sent a command ORed with zero page $E0 and no LISTEN.
+- src/kernal/iec/chkin_iec.s, ckout_iec.s (2026-10-15): CHKIN and CHKOUT take the secondary
+  address from SAT, not from LAT, the logical file numbers.
+- src/kernal/iec/tksa.s (2026-10-15): TKSA sends the secondary address it is given, without
+  ORing $90 into it (upstream issue #116).
+- src/kernal/iec/iec_tx_byte.s (2026-10-15): a data byte that no listener holds DATA for
+  sets ST to $80 (device not present) and returns, instead of waiting forever.
+- src/kernal/iec/close_iec.s (2026-10-15): a CLOSE that finds no device sets ST to $80
+  (device not present), and still frees the file number.
+- src/kernal/iec/unlsn.s, untlk.s (2026-10-15): UNLSN and UNTLK end with CLK, DATA, and ATN
+  released; UNLSN left CLK pulled, and UNTLK waited for a talker to pull CLK, which after
+  UNTALK none does, and then left CLK pulled.
+- src/kernal/iec/iec_return.s (2026-10-15): a serial routine that finds no device releases
+  CLK, DATA, and ATN; it left CLK pulled.
+- src/,,config_mc64.s, src/aliases/,aliases_hardware_arnitech.s, src/kernal/arnitech/
+  (new), Makefile, src/kernal/init/fda3.ioinit.s, CONFIG.md (2026-10-17): a new option,
+  ARNITECH_CONTROLLER, on in the mc64 configuration only. IOINIT sets CIA #1's TOD on 50 Hz
+  and, if the Arnitech controller's signature is at $DE80, from the controller's clock. The
+  Arnitech jump table at $FF00 wraps the controller's registers: "ARNI", a version, an entry
+  count, and JMPs from $FF06 to find a Card by its type and to set the TOD.
+- NOTICE: this file.
+
+The licence terms are unchanged; see LICENSE, COPYING, and COPYING.LESSER.

src/,,config_mc64.s

@@ -0,0 +1,133 @@
+
+;; #CONFIG# ID $6D ; should be 1 byte, different for each config file!
+
+;
+; Please read CONFIG.md before modifying this file!
+;
+
+; Idea:
+; The Firmware of arnitech's mc64 computers, a Minecraft mod
+; Same as the 'c64' configuration, except:
+; - the banner names mc64
+; - BCD_SAFE_INTERRUPTS is off, for IRQ entry timing closer to the original
+; - ARNITECH_CONTROLLER: IOINIT sets CIA1's TOD on 50 Hz and from the Arnitech controller's clock,
+;   and the Arnitech jump table is at $FF00 (src/kernal/arnitech)
+
+
+
+; --- Hardware platform and brand
+
+;; #CONFIG# PLATFORM_COMMODORE_64      YES
+;; #CONFIG# BRAND_CUSTOM               "MC64"
+
+
+; --- Processor instruction set
+
+;; #CONFIG# CPU_MOS_6502               YES
+;; #CONFIG# CPU_DTV_6502               NO
+;; #CONFIG# CPU_RCW_65C02              NO
+;; #CONFIG# CPU_WDC_65C02              NO
+;; #CONFIG# CPU_WDC_65816              NO
+;; #CONFIG# CPU_CSG_65CE02             NO
+
+
+; --- Memory model
+
+;; #CONFIG# MEMORY_MODEL_38K           YES
+;; #CONFIG# MEMORY_MODEL_46K           NO
+;; #CONFIG# MEMORY_MODEL_50K           NO
+;; #CONFIG# MEMORY_MODEL_60K           NO
+
+
+; --- IEC bus configuration
+
+;; #CONFIG# IEC                        YES
+;; #CONFIG# IEC_DOLPHINDOS             NO
+;; #CONFIG# IEC_DOLPHINDOS_FAST        NO
+;; #CONFIG# IEC_JIFFYDOS               NO
+;; #CONFIG# IEC_JIFFYDOS_BLANK         NO
+
+
+; --- Tape deck configuration
+
+;; #CONFIG# TAPE_NORMAL                YES
+;; #CONFIG# TAPE_TURBO                 NO
+;; #CONFIG# TAPE_AUTODETECT            NO
+;; #CONFIG# TAPE_NO_KEY_SENSE          NO
+;; #CONFIG# TAPE_NO_MOTOR_CONTROL      NO
+
+
+; --- Sound support
+
+;; #CONFIG# SID_2ND_ADDRESS            NO
+;; #CONFIG# SID_3RD_ADDRESS            NO
+;; #CONFIG# SID_D4XX                   NO
+;; #CONFIG# SID_D5XX                   NO
+;; #CONFIG# SID_D6XX                   NO
+;; #CONFIG# SID_D7XX                   NO
+
+
+; --- Keyboard settings
+
+;; #CONFIG# KEYBOARD_C128              NO
+;; #CONFIG# KEYBOARD_C128_CAPS_LOCK    NO
+;; #CONFIG# KEY_REPEAT_DEFAULT         NO
+;; #CONFIG# KEY_REPEAT_ALWAYS          NO
+;; #CONFIG# KEY_FAST_SCAN              YES
+;; #CONFIG# JOY1_CURSOR                YES
+;; #CONFIG# JOY2_CURSOR                YES
+
+;; #CONFIG# PROGRAMMABLE_KEYS          YES
+
+;; #CONFIG# KEYCMD_RUN                 "\5FL"
+
+;; #CONFIG# KEYCMD_F1                  "@8$"
+;; #CONFIG# KEYCMD_F2                  "LOAD"
+;; #CONFIG# KEYCMD_F3                  "@9$"
+;; #CONFIG# KEYCMD_F4                  "RUN:"
+;; #CONFIG# KEYCMD_F5                  "@10$"
+;; #CONFIG# KEYCMD_F6                  NO
+;; #CONFIG# KEYCMD_F7                  "@11$"
+;; #CONFIG# KEYCMD_F8                  NO
+
+;; #CONFIG# KEYCMD_HELP                "LIST"
+
+
+; --- Screen editor
+
+;; #CONFIG# EDIT_STOPQUOTE             YES
+
+
+; --- Software features
+
+;; #CONFIG# PANIC_SCREEN               YES
+;; #CONFIG# DOS_WEDGE                  NO
+;; #CONFIG# TAPE_WEDGE                 NO
+;; #CONFIG# TAPE_HEAD_ALIGN            NO
+;; #CONFIG# BCD_SAFE_INTERRUPTS        NO
+;; #CONFIG# ARNITECH_CONTROLLER        YES
+
+
+; --- BASIC features
+
+;; #CONFIG# ORIGINAL_UNPATCHED_BASIC   YES
+;; #CONFIG# TRANSCENDENTAL_FUNCTIONS   YES
+
+
+; --- Eye candy
+
+;; #CONFIG# COLORS_BRAND               NO
+;; #CONFIG# BANNER_SIMPLE              YES
+;; #CONFIG# BANNER_FANCY               NO
+;; #CONFIG# SHOW_FEATURES              YES
+
+
+; --- Debug options
+
+;; #CONFIG# DBG_STUBS_BRK              NO
+;; #CONFIG# DBG_PRINTF                 NO
+
+
+; --- Other
+
+;; #CONFIG# COMPRESSION_LVL_2          NO

src/aliases/,aliases_hardware_arnitech.s

@@ -0,0 +1,26 @@
+
+;
+; Names of the Arnitech controller's registers, on the expansion port's I/O1 (mc64 only)
+;
+; See arnitech's ADR 0023, "The Arnitech controller answers $DE80-$DE9F, and six Card windows
+; follow it" (https://git.susdog.de/chris/arnitech, docs/adr/0023-arnitech-controller-register-map.md)
+;
+
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+	!addr ARNITECH_SIGNATURE   = $DE80  ; "ARNI", 4 bytes
+	!addr ARNITECH_VERSION     = $DE84
+	!addr ARNITECH_SLOT_COUNT  = $DE85  ; Card slots in this Case
+	!addr ARNITECH_IRQ_STATUS  = $DE86
+	!addr ARNITECH_IRQ_MASK    = $DE87
+	!addr ARNITECH_SLOT_TABLE  = $DE88  ; the type of the Card in slots 0-5, $00 for none
+
+	!addr ARNITECH_CLOCK_LATCH = $DE90  ; a read copies the clock into $DE91-$DE9E
+	!addr ARNITECH_CLOCK_TEN   = $DE91  ; real time as CIA1's TOD reads it: tenths,
+	!addr ARNITECH_CLOCK_SEC   = $DE92  ; seconds,
+	!addr ARNITECH_CLOCK_MIN   = $DE93  ; minutes,
+	!addr ARNITECH_CLOCK_HRS   = $DE94  ; hours, BCD 1-12, bit 7 PM
+
+	!addr ARNITECH_CARD_WINDOW = $DEA0  ; slot n's Card window at $DEA0 + 16 * n
+}

src/kernal/arnitech/arnitech_controller.s

@@ -0,0 +1,64 @@
+;; #LAYOUT# STD *        #TAKE
+;; #LAYOUT# *   *        #IGNORE
+
+;
+; The Arnitech controller (mc64 only, arnitech's ADR 0023): its signature and its Slot table
+;
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+;
+; Whether the controller answers: its signature "ARNI" at $DE80, compared with the jump table's.
+; Out: carry clear if it does, carry set if not. A and X are not kept, Y is.
+;
+
+arnitech_check_signature:
+
+	ldx #$03
+@1:
+	lda ARNITECH_SIGNATURE, x
+	cmp arnitech_jumptable, x
+	bne @2
+	dex
+	bpl @1
+
+	clc
+	rts
+@2:
+	sec
+	rts
+
+;
+; ARNI_FINDCARD, $FF06: see ff00.arnitech_jumptable.s
+;
+
+arnitech_find_card:
+
+	pha
+	jsr arnitech_check_signature
+	pla
+	bcs @2                             ; no controller
+
+	ldx #$00
+@1:
+	cpx ARNITECH_SLOT_COUNT
+	bcs @2                             ; past the last slot, carry set
+	cmp ARNITECH_SLOT_TABLE, x
+	beq @3
+	inx
+	bne @1                             ; always taken
+@2:
+	rts
+@3:
+	txa
+	pha
+	asl
+	asl
+	asl
+	asl                                ; 16 * slot
+	clc
+	adc #<ARNITECH_CARD_WINDOW
+	tax
+	pla
+	rts                                ; carry clear
+}

src/kernal/arnitech/arnitech_tod.s

@@ -0,0 +1,58 @@
+;; #LAYOUT# STD *        #TAKE
+;; #LAYOUT# *   *        #IGNORE
+
+;
+; CIA1's TOD from the Arnitech controller's real time (mc64 only, arnitech's ADR 0023)
+;
+; The controller lays its time out as the TOD reads it, so the copy goes hours first, which stops
+; the TOD, and tenths last, which starts it. The CIA flips the PM bit when an hour of 12 is
+; written (VICE does so too), so an hour of 12 has bit 7 flipped first.
+;
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+;
+; ARNI_SETTOD, $FF09: see ff00.arnitech_jumptable.s
+;
+
+arnitech_set_tod:
+
+	lda CIA1_CRA
+	ora #$80                           ; TOD on 50 Hz, the mc64's mains
+	sta CIA1_CRA
+
+	; FALLTHROUGH
+
+;
+; The copy alone, for IOINIT, which has set CRA already.
+; Out: carry clear if set, carry set if no controller answers. A and X are not kept, Y is.
+;
+
+arnitech_tod_from_clock:
+
+	jsr arnitech_check_signature
+	bcs @2
+
+	lda ARNITECH_CLOCK_LATCH           ; copies the clock into $DE91-$DE9E
+
+	ldx ARNITECH_CLOCK_HRS
+	txa
+	and #$7F
+	cmp #$12
+	bne @1
+	txa
+	eor #$80                           ; the CIA flips it back
+	tax
+@1:
+	stx CIA1_TODHRS                    ; stops the TOD
+	lda ARNITECH_CLOCK_MIN
+	sta CIA1_TODMIN
+	lda ARNITECH_CLOCK_SEC
+	sta CIA1_TODSEC
+	lda ARNITECH_CLOCK_TEN
+	sta CIA1_TODTEN                    ; starts it
+
+	clc
+@2:
+	rts
+}

src/kernal/arnitech/ff00.arnitech_jumptable.s

@@ -0,0 +1,40 @@
+;; #LAYOUT# STD *        #TAKE
+;; #LAYOUT# *   *        #IGNORE
+
+;
+; The Arnitech jump table (mc64 only): thin wrappers over the Arnitech controller's registers
+; (arnitech's ADR 0023), at fixed addresses. Software finds it by reading "ARNI" at $FF00 with
+; the KERNAL banked in; on any other KERNAL it uses the registers themselves, which work the same.
+; Entries are only ever added, after the last, with the version and count raised; $FF48-$FF80
+; stay clear, for the stock IRQ entry, CINT, and the KERNAL revision byte.
+;
+; $FF00-$FF03  "ARNI"
+; $FF04        version of the table, $01
+; $FF05        number of entries
+;
+; $FF06  ARNI_FINDCARD - finds the first Card slot holding a Card of a given type
+;        In:  A = the Card's type ($01 Redstone Card, $02 Internet Card; $00 finds an empty slot)
+;        Out: carry clear if found: A = the slot (0-5), X = the low byte of its Card window
+;             ($DEA0 + 16 * slot, so LDA $DE00,X reads the window's first byte);
+;             carry set if no slot holds one, or no controller answers (a Cartridge switched it off)
+;        Y is kept; A and X are not, when none is found
+;
+; $FF09  ARNI_SETTOD - sets CIA1's TOD from the controller's real time, as IOINIT does at boot
+;        In:  nothing; CIA1's CRB bit 7 must be 0, or the time goes into the TOD alarm
+;        Out: carry clear if set: the TOD on 50 Hz (CIA1 CRA bit 7) and started at the time the
+;             controller's clock latch read; carry set if no controller answers, with the TOD
+;             untouched but on 50 Hz all the same
+;        A and X are not kept, Y is
+;
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+arnitech_jumptable:
+
+	!byte $41, $52, $4E, $49           ; "ARNI"
+	!byte $01                          ; version
+	!byte $02                          ; entries
+
+	jmp arnitech_find_card             ; $FF06
+	jmp arnitech_set_tod               ; $FF09
+}

src/kernal/iec/chkin_iec.s

@@ -14,7 +14,7 @@ chkin_iec:
 
 	; Fail if the file is open for writing (secondary address 1)
 	
-	lda LAT, Y
+	lda SAT, Y
 	cmp #$01
 	+beq chkin_file_not_input
 
@@ -24,7 +24,7 @@ chkin_iec:
 	jsr TALK
 	+bcs chkinout_device_not_present
 
-	lda LAT, Y
+	lda SAT, Y
 	ora #$60
 	jsr TKSA
 	+bcs chkinout_device_not_present

src/kernal/iec/ciout.s

@@ -28,9 +28,10 @@ CIOUT:
 	
 ciout_store_in_buffer:
 
-	; Store in the buffer data to be sent next, return
+	; Store in the buffer data to be sent next, return; iec_tx_byte
+	; sends the byte from TBTCNT, so that is our buffer, not BSOUR
 	pla
-	sta BSOUR
+	sta TBTCNT
 	rts
 	
 ciout_send_byte:

src/kernal/iec/ckout_iec.s

@@ -14,7 +14,7 @@ ckout_iec:
 
 	; Fail if the file is open for reading (secondary address 0)
 	
-	lda LAT, Y
+	lda SAT, Y
 	+beq ckout_file_not_output
 
 	; Send LISTEN + SECOND first
@@ -23,7 +23,7 @@ ckout_iec:
 	jsr LISTEN
 	+bcs chkinout_device_not_present
 
-	lda LAT, Y
+	lda SAT, Y
 	ora #$60
 	jsr SECOND
 	+bcs chkinout_device_not_present

src/kernal/iec/close_iec.s

@@ -23,11 +23,23 @@ close_iec:
 	jsr iec_close_load 
 	jmp close_remove_from_table
 @1:
-	ora $E0 ; CLOSE command
+	; LISTEN, CLOSE, UNLISTEN - see https://www.pagetable.com/?p=1031
+	lda FAT, y
+	jsr LISTEN
+	bcs close_iec_not_present
+	lda SAT, y
+	ora #$E0 ; CLOSE command
 	sta TBTCNT
 	jsr iec_tx_command
-	bcs close_iec_end
+	bcs close_iec_not_present
 	jsr iec_tx_command_finalize
+	jsr UNLSN
+	jmp close_remove_from_table
+
+close_iec_not_present:
+
+	; The file is closed all the same; READST says device not present
+	jsr kernalstatus_DEVICE_NOT_FOUND
 
 	; FALLTROUGH
 

src/kernal/iec/iec_return.s

@@ -36,8 +36,8 @@ iec_return_success:
 
 iec_return_DEVICE_NOT_FOUND:
 
-	; Set IEC line to normal idle state
+	; Nobody answers: release all lines, so the bus is idle - see https://www.pagetable.com/?p=1135
-	jsr iec_set_idle
+	jsr iec_release_atn_clk_data
 
 	; BSOUR is certainly not valid anymore
 	lda #$00

src/kernal/iec/iec_tx_byte.s

@@ -51,6 +51,17 @@ iec_tx_byte:
 	+phx_trash_a
 	+phy_trash_a
 
+	; A listener holds DATA until we release CLK; if nobody pulls it
+	; within 256us, no device is present - see https://www.pagetable.com/?p=1135
+	ldx #$18
+@0:
+	lda CIA2_PRA
+	bpl @1                             ; branch if DATA is pulled
+	dex
+	bne @0
+	jsr kernalstatus_DEVICE_NOT_FOUND
+	jmp iec_return_DEVICE_NOT_FOUND
+@1:
 	; Notify all devices that we are going to send a byte
 	; and it is going to be a data byte (released ATN)
 	jsr iec_release_atn_clk_data

src/kernal/iec/tksa.s

@@ -28,8 +28,6 @@ TKSA:
 	; - https://www.lemon64.com/forum/viewtopic.php?t=57694&sid=531ba3592bcffadef2ac8b9162f2e529
 	; - https://www.pagetable.com/?p=1031 (Kernal API description)
 
-	ora #$90
-
 	jmp common_untlk_tksa
 
 } else {

src/kernal/iec/unlsn.s

@@ -42,7 +42,15 @@ UNLSN:
 	; Buffer empty, send the command
 	lda #$3F
 
-	jmp common_open_close_unlsn_second
+common_unlsn_untlk: ; common part of UNLSN and UNTLK
+
+	jsr common_open_close_unlsn_second
+	bcs @1
+
+	; The transmission is over: release CLK and DATA too, so the bus is idle - see https://www.pagetable.com/?p=1135
+	jmp iec_release_clk_data
+@1:
+	rts
 
 } else {
 

src/kernal/iec/untlk.s

@@ -39,10 +39,11 @@ UNTLK:
 	sta IECPROTO
 }
 
-	; Buffer empty, send the command
+	; Buffer empty, send the command; the talker releases the bus - see https://www.pagetable.com/?p=1031
 	lda #$5F
+	jmp common_unlsn_untlk
 
-common_untlk_tksa: ; common part of UNTLK and TKSA
+common_untlk_tksa: ; the rest of TKSA
 
 	; XXX - for TKSA, is it really the right place to do a turnaround? I have some doubts
 	; (it forces us to send the TKSA command 'manually' sometimes), but

src/kernal/init/fda3.ioinit.s

@@ -168,8 +168,18 @@ IOINIT_skip_DOS:
 	jsr setup_irq_timer
 
 	; Enable timer A to run continuously (http://codebase64.org/doku.php?id=base:timerinterrupts)
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+	; ... with the TOD on 50 Hz, the mc64's mains, set from the Arnitech controller's clock
+	ldx #$91
+	stx CIA1_CRA     ; $DC0E
+	jsr arnitech_tod_from_clock
+
+} else {
+
 	ldx #$11
 	stx CIA1_CRA     ; $DC0E
+}
 
 	; Enable timer interrupt
 	ldx #$81