A score table needs a clear answer for ties, a full table and the player who just misses the cut.
Use it in a project
Maintain up to four descending unsigned byte scores with associated byte tags. Insert after existing equal scores. Return RANK 0–3 and INSERTED=1 when retained; otherwise RANK=255. COUNT>4 is invalid. Entries beyond COUNT are unused; the existing prefix must be sorted.
Include component.inc once (MOS callers include the shared 6502 implementation through it). Reserve the public fields in this exact order: RANK, INSERTED, VALID, SCORE, TAG, COUNT, S0, S1, S2, S3, I0, I1, I2, I3. They occupy 14 contiguous bytes. Also reserve the private workspace: T0, T1, T2, T3, EXPR_SAVE (5 bytes). Array names in the explanation refer to the numbered consecutive bindings, such as C0, C1 and so on.
Call high_score_insertion_init once at the intended reset boundary. It clears inputs as well as outputs and workspace. Set your starting state and configuration afterwards, then call high_score_insertion_step whenever the described event occurs. The helper reads no device, waits for no frame and installs no interrupt handler.
| Ownership | Fields |
|---|---|
| Retain between calls | COUNT, S0..S3 and I0..I3 |
| Supply before service | SCORE and TAG |
| Read after service | RANK, INSERTED and VALID |
Find the first strictly smaller score, then move the tail backwards so no source entry is overwritten before it has been copied.
Reusable initialisation and service
; SPDX-License-Identifier: MIT
; Insert into a High-score Table. See README.md for the byte interface and ownership.
; init clears the public fields and private workspace; set inputs afterwards.
high_score_insertion_init:
move.b #0,d0
move.b d0,RANK
move.b d0,INSERTED
move.b d0,VALID
move.b d0,SCORE
move.b d0,TAG
move.b d0,COUNT
move.b d0,S0
move.b d0,S1
move.b d0,S2
move.b d0,S3
move.b d0,I0
move.b d0,I1
move.b d0,I2
move.b d0,I3
move.b d0,T0
move.b d0,T1
move.b d0,T2
move.b d0,T3
move.b d0,EXPR_SAVE
rts
high_score_insertion_step:
; RANK = 255
move.b #255,d0
move.b d0,RANK
; INSERTED = 0
move.b #0,d0
move.b d0,INSERTED
; VALID = 0
move.b #0,d0
move.b d0,VALID
; if COUNT > 4:
move.b COUNT,d0
cmp.b #4,d0
bhi high_score_insertion_L1
jmp high_score_insertion_L2
high_score_insertion_L1:
; return
rts
jmp high_score_insertion_L3
high_score_insertion_L2:
high_score_insertion_L3:
; VALID = 1
move.b #1,d0
move.b d0,VALID
; T0 = 0
move.b #0,d0
move.b d0,T0
; while T0 < COUNT:
high_score_insertion_L4:
move.b T0,d0
move.b COUNT,d1
cmp.b d1,d0
bcs high_score_insertion_L5
jmp high_score_insertion_L6
high_score_insertion_L5:
; T1 = S[T0]
moveq #0,d1
move.b T0,d1
lea S0,a0
move.b 0(a0,d1.w),d0
move.b d0,T1
; if SCORE > T1:
move.b SCORE,d0
move.b T1,d1
cmp.b d1,d0
bhi high_score_insertion_L7
jmp high_score_insertion_L8
high_score_insertion_L7:
; break
jmp high_score_insertion_L6
jmp high_score_insertion_L9
high_score_insertion_L8:
high_score_insertion_L9:
; T0 = T0 + 1
move.b T0,d0
add.b #1,d0
move.b d0,T0
jmp high_score_insertion_L4
high_score_insertion_L6:
; if T0 >= 4:
move.b T0,d0
cmp.b #4,d0
bcc high_score_insertion_L10
jmp high_score_insertion_L11
high_score_insertion_L10:
; return
rts
jmp high_score_insertion_L12
high_score_insertion_L11:
high_score_insertion_L12:
; RANK = T0
move.b T0,d0
move.b d0,RANK
; if COUNT < 4:
move.b COUNT,d0
cmp.b #4,d0
bcs high_score_insertion_L13
jmp high_score_insertion_L14
high_score_insertion_L13:
; COUNT = COUNT + 1
move.b COUNT,d0
add.b #1,d0
move.b d0,COUNT
jmp high_score_insertion_L15
high_score_insertion_L14:
high_score_insertion_L15:
; T1 = COUNT - 1
move.b COUNT,d0
sub.b #1,d0
move.b d0,T1
; while T1 > T0:
high_score_insertion_L16:
move.b T1,d0
move.b T0,d1
cmp.b d1,d0
bhi high_score_insertion_L17
jmp high_score_insertion_L18
high_score_insertion_L17:
; T2 = T1 - 1
move.b T1,d0
sub.b #1,d0
move.b d0,T2
; T3 = S[T2]
moveq #0,d1
move.b T2,d1
lea S0,a0
move.b 0(a0,d1.w),d0
move.b d0,T3
; S[T1] = T3
move.b T3,d0
move.b d0,d2
moveq #0,d1
move.b T1,d1
lea S0,a0
move.b d2,0(a0,d1.w)
; T3 = I[T2]
moveq #0,d1
move.b T2,d1
lea I0,a0
move.b 0(a0,d1.w),d0
move.b d0,T3
; I[T1] = T3
move.b T3,d0
move.b d0,d2
moveq #0,d1
move.b T1,d1
lea I0,a0
move.b d2,0(a0,d1.w)
; T1 = T1 - 1
move.b T1,d0
sub.b #1,d0
move.b d0,T1
jmp high_score_insertion_L16
high_score_insertion_L18:
; S[T0] = SCORE
move.b SCORE,d0
move.b d0,d2
moveq #0,d1
move.b T0,d1
lea S0,a0
move.b d2,0(a0,d1.w)
; I[T0] = TAG
move.b TAG,d0
move.b d0,d2
moveq #0,d1
move.b T0,d1
lea I0,a0
move.b d2,0(a0,d1.w)
; INSERTED = 1
move.b #1,d0
move.b d0,INSERTED
rts
component_end:Machine contract
D0–D3/A0–A1/CCR may change; D4–D7/A2–A6 are preserved. A direct BSR/JSR needs four return-address stack bytes. The helper makes no nested calls and adds no other stack use. Its named scratch is private workspace, not a pointer, a ROM variable or shared zero-page space that the game may borrow concurrently. The samples use fixed symbol bindings. Scope or rename every label and binding, including the component_end measurement marker, and allocate a separate block for each independent instance. Different helpers can also use common field names, so combining them needs separate namespaces or explicitly renamed bindings. Give each block one mutation owner.
The A500 OCS diagnostic cold-boots an OFS disk, owns the Copper and bitplane and disables interrupt/DMA sources. The helper does not take over hardware or allocate Chip RAM.
Adapt the caller
demo.asm supplies the bindings and include order. exercise.inc first runs table cases, then a separate client retaining state between calls. A game can call the public step entry directly and remove the diagnostic packet and display. Do not copy the diagnostic’s hardware takeover into an existing game loop.
Build with make ASM198X=/path/to/asm198x and BUILD198X=/path/to/build198x. The Makefile produces normal, custom, deliberately wrong and repaired programs. Tools must already be installed; the sample downloads nothing.
Bindings and include order
section code,code_c
CUSTOM = 0
BROKEN = 0
COYOTE_STEPS = 4
BUFFER_STEPS = 4
TEXT_CAP = 8
PROPERTY_COUNT = 16
STREAM_BYTES = 13
CRC_POLY = 7
include "caller.inc"
include "exercise.inc"
component_start:
include "component.inc"
even
include "data.inc"
include "cases.inc"
even
include "display.inc"
include "../../framework/turn-deadline/font.inc"
code_end:
STATE:
RANK: dc.b 0
INSERTED: dc.b 0
VALID: dc.b 0
SCORE: dc.b 0
TAG: dc.b 0
COUNT: dc.b 0
S0: dc.b 0
S1: dc.b 0
S2: dc.b 0
S3: dc.b 0
I0: dc.b 0
I1: dc.b 0
I2: dc.b 0
I3: dc.b 0
T0: dc.b 0
T1: dc.b 0
T2: dc.b 0
T3: dc.b 0
EXPR_SAVE: dc.b 0
even
ready: dc.w 0
preview: dcb.b 8,0
OUTPUT: dcb.b 1300,0
even
signature: dc.b "198XTOOLKIT0000",0
even
copperlist:
dc.w $08e,$2c81,$090,$2cc1,$092,$0038,$094,$00d0
dc.w $100,$1200,$102,0,$104,0,$108,0,$10a,0
dc.w $180,$012,$182,$fff
copbpl:
dc.w $0e0,0,$0e2,0
dc.w $ffff,$fffe
plane: dcb.b 10240,0A client retaining state between calls
preview_rules:
ifne CUSTOM
; SCORE = 255
move.b #255,d0
move.b d0,SCORE
; TAG = 4
move.b #4,d0
move.b d0,TAG
ifne BROKEN
; SCORE = 0
move.b #0,d0
move.b d0,SCORE
endif
bsr checked_step
bsr emit_state
; SCORE = 0
move.b #0,d0
move.b d0,SCORE
; TAG = 5
move.b #5,d0
move.b d0,TAG
ifne BROKEN
; SCORE = 0
move.b #0,d0
move.b d0,SCORE
endif
bsr checked_step
bsr emit_state
rts
else
; SCORE = 20
move.b #20,d0
move.b d0,SCORE
; TAG = 1
move.b #1,d0
move.b d0,TAG
ifne BROKEN
; SCORE = 0
move.b #0,d0
move.b d0,SCORE
endif
bsr checked_step
bsr emit_state
; SCORE = 40
move.b #40,d0
move.b d0,SCORE
; TAG = 2
move.b #2,d0
move.b d0,TAG
ifne BROKEN
; SCORE = 0
move.b #0,d0
move.b d0,SCORE
endif
bsr checked_step
bsr emit_state
; SCORE = 40
move.b #40,d0
move.b d0,SCORE
; TAG = 3
move.b #3,d0
move.b d0,TAG
ifne BROKEN
; SCORE = 0
move.b #0,d0
move.b d0,SCORE
endif
bsr checked_step
bsr emit_state
endif
rtsCustomise it
Retain the highest possible byte score and a zero score. The maintained custom caller changes its inputs or client sequence rather than hiding a different implementation behind the same label. Compare every state of the two clients, not only their final display.
Custom client selection
section code,code_c
CUSTOM = 1
BROKEN = 0
COYOTE_STEPS = 2
BUFFER_STEPS = 2
TEXT_CAP = 4
PROPERTY_COUNT = 16
STREAM_BYTES = 13
CRC_POLY = 49
include "caller.inc"
include "exercise.inc"
component_start:
include "component.inc"
even
include "data.inc"
include "cases.inc"
even
include "display.inc"
include "../../framework/turn-deadline/font.inc"
code_end:
STATE:
RANK: dc.b 0
INSERTED: dc.b 0
VALID: dc.b 0
SCORE: dc.b 0
TAG: dc.b 0
COUNT: dc.b 0
S0: dc.b 0
S1: dc.b 0
S2: dc.b 0
S3: dc.b 0
I0: dc.b 0
I1: dc.b 0
I2: dc.b 0
I3: dc.b 0
T0: dc.b 0
T1: dc.b 0
T2: dc.b 0
T3: dc.b 0
EXPR_SAVE: dc.b 0
even
ready: dc.w 0
preview: dcb.b 8,0
OUTPUT: dcb.b 1300,0
even
signature: dc.b "198XTOOLKIT0000",0
even
copperlist:
dc.w $08e,$2c81,$090,$2cc1,$092,$0038,$094,$00d0
dc.w $100,$1200,$102,0,$104,0,$108,0,$10a,0
dc.w $180,$012,$182,$fff
copbpl:
dc.w $0e0,0,$0e2,0
dc.w $ffff,$fffe
plane: dcb.b 10240,0The custom diagnostic row is 01 01 01 00 05 02 FF 00. The full client trace in the source explains how it gets there.
Mistake and repair
The wrong caller clears the achieved score before inserting it. The ordering routine cannot recover that lost value. Pass the completed score before resetting gameplay state.
The BROKEN branch lives in the sequential client, not the reusable helper. wrong.asm selects it; repaired.asm restores the normal call sequence. The repaired executable matches the normal program (for Spectrum, compare loaded CODE rather than the tape filename).
Select the deliberately wrong client
section code,code_c
CUSTOM = 0
BROKEN = 1
COYOTE_STEPS = 4
BUFFER_STEPS = 4
TEXT_CAP = 8
PROPERTY_COUNT = 16
STREAM_BYTES = 13
CRC_POLY = 7
include "caller.inc"
include "exercise.inc"
component_start:
include "component.inc"
even
include "data.inc"
include "cases.inc"
even
include "display.inc"
include "../../framework/turn-deadline/font.inc"
code_end:
STATE:
RANK: dc.b 0
INSERTED: dc.b 0
VALID: dc.b 0
SCORE: dc.b 0
TAG: dc.b 0
COUNT: dc.b 0
S0: dc.b 0
S1: dc.b 0
S2: dc.b 0
S3: dc.b 0
I0: dc.b 0
I1: dc.b 0
I2: dc.b 0
I3: dc.b 0
T0: dc.b 0
T1: dc.b 0
T2: dc.b 0
T3: dc.b 0
EXPR_SAVE: dc.b 0
even
ready: dc.w 0
preview: dcb.b 8,0
OUTPUT: dcb.b 1300,0
even
signature: dc.b "198XTOOLKIT0000",0
even
copperlist:
dc.w $08e,$2c81,$090,$2cc1,$092,$0038,$094,$00d0
dc.w $100,$1200,$102,0,$104,0,$108,0,$10a,0
dc.w $180,$012,$182,$fff
copbpl:
dc.w $0e0,0,$0e2,0
dc.w $ffff,$fffe
plane: dcb.b 10240,0
Cost and alternatives
The measured helper extent is 514 code bytes; public state is 14 bytes and private scratch is 5 bytes. There are no immutable helper tables. Caller data, the test cases, return-address stack, alignment and display buffers cost additional space. These are assembled sizes, not cycle measurements.
Four comparisons and at most three pair moves. Insertion is easier to audit than sorting the whole table after every result.
Scores are one byte and tags are identifiers, not name strings. Wider scores need a multi-byte comparison; permanent storage is a separate concern.
Execution evidence
Four variants run on A500 OCS PAL, Kickstart1.3 OFS cold boot, using Asm198x 0.0.72, Emu198x 0.44.2 and Build198x 0.2.9. Each executes 64 boundary/varied/error table cases, dirty initialisation and the separate retained-state client. An independent mathematical/container model checks every public byte after every call. This is bounded example coverage, not exhaustive correctness for every possible state.
The records retain loaded immutable code, completion, register sentinels, full packets, source/tool/firmware hashes and captures. The public gate validates these retained observations and rejects altered evidence; it does not run restricted firmware. No firmware is distributed. The eight displayed bytes are the first eight public fields, zero-padded when shorter; the packet includes every field.
Where it fits
Score counters: Store the final score before starting a new run.