Tecmo Super Bowl (bruddog's commented disassembly of the US NES release)

Tecmo Super Bowl stores each player rating as a 4-bit index from 0 to 15, two to a byte. The player data screen shows an index as 6, 13, 19, 25, 31, 38, 44, 50, 56, 63, 69, 75, 81, 88, 94, or 100. When the game reads a rating, it adds the player's condition (bad 0, average 1, good 2, excellent 3) less 1 and clamps the result to 0–15, so a bad player plays one step down and an excellent one two steps up. tecmo-super-bowl/ratings

About: Tecmo Super Bowl Player ratings

{
 "steps": 16,
 "shown": [
  6,
  13,
  19,
  25,
  31,
  38,
  44,
  50,
  56,
  63,
  69,
  75,
  81,
  88,
  94,
  100
 ],
 "condition_steps": {
  "bad": -1,
  "average": 0,
  "good": 1,
  "excellent": 2
 }
}

The displayed numbers are binary-coded decimal words, read here as decimal. GET_PLAYER_COND_INJURY_STATUS returns the condition as two bits (Bank31_fixed_bank.asm L5145-L5148). The ratings named in constants_variables/skill_indexes.asm are rushing power (RP), running speed (RS), max speed (MS), and hitting power (HP) for everyone, plus passing speed, pass control (PC), passing accuracy, and avoid pass block for quarterbacks; ball control and reception (REC) for ball carriers; interception (INT) and quickness for defenders; and kicking ratings for kickers and punters.

Cited by: Player ratings, Tecmo Super Bowl

On the field each player carries a current speed and a max speed. The max speed (MS) rating picks a max speed of 21 to 36 for an offensive player and 37 to 52 for a defender, one per step. Running speed (RS) sets the starting current speed, 14 to 29, and rushing power (RP) sets a countdown of 13 frames at step 0 down to 1 at steps 14 and 15. On each frame a player is moving, the countdown drops by 1; when it reaches 0 it reloads, and the current speed rises by 1 unless it has reached max speed. A computer-controlled defense facing a human-controlled offense loads differently: it adds CPU_DEF_MS_BOOST to its max speed and to its RS and RP steps, capping the steps at 15. tecmo-super-bowl/speed

About: Tecmo Super Bowl Player ratings

{
 "max_speed_offense": [
  21,
  36
 ],
 "max_speed_defense": [
  37,
  52
 ],
 "start_speed": [
  14,
  29
 ],
 "rp_frames": [
  13,
  12,
  11,
  10,
  9,
  8,
  7,
  6,
  5,
  4,
  3,
  3,
  2,
  2,
  1,
  1
 ]
}

At the same MS rating a defender's max speed is 16 higher than a ball carrier's. The speed unit isn't named in the code read here. The P2 side mirrors the boost check (Bank27_misc.asm L1186-L1196). SET_COMPUTER_BOOST_VALUES (L188-L267) sets CPU_DEF_MS_BOOST from a table or to 0; the atlas hasn't claimed when each applies.

Cited by: Player ratings, Tecmo Super Bowl

When two computer-controlled players collide, the game compares their hitting power (HP), loaded from a table at 4 per rating step (0 to 60). If neither leads by 16 (4 steps), they hold for 8 frames plus random waits of up to 255, 255, and 63 frames, and one random bit picks the winner. With a lead of 16 to 31, the stronger player wins when a random byte is under 170 (computed: 66%); otherwise they grapple as before. With a lead of 32 or more, the stronger player wins on a byte under 205 (computed: 80%); otherwise they hold 64 frames and then grapple. tecmo-super-bowl/grapple-com

About: Tecmo Super Bowl Button mashing

{
 "hp": [
  0,
  60
 ],
 "hp_per_step": 4,
 "leads": [
  16,
  32
 ],
 "win_chance": {
  "lead_16": "170/256",
  "lead_32": "205/256"
 }
}

The code's comments give some of these chances as 60% and 25%; the comparisons give 170/256 and 205/256 for a win. Leads are signed: the defense's thresholds $F0 and $E0 plus 1 make the same 16 and 32 from the other side. The comments call 16 HP "25 HP" and 32 "50 HP", on the 6-to-100 display scale. After a win, further random bytes decide whether the winner stays on his feet and how far the loser is thrown.

Cited by: Button mashing, Tecmo Super Bowl

An ordinary collision (not a dive or a chop block) between a human-controlled and a computer-controlled player goes to MAN_VS_COM_POPCORN_CHECK. If the human player's HP is at least 32 higher (8 rating steps), the computer player is thrown at once; otherwise both hold for 64 frames while the game counts the human's A presses, and 2 or more throw the computer player, and fewer throw the human. Between two human players, both players' presses count over the same 64 frames. The defender wins with at least as many presses as the offensive player; if neither pressed, both go down. tecmo-super-bowl/grapple-man

About: Tecmo Super Bowl Button mashing

{
 "popcorn_lead": 32,
 "hold_frames": 64,
 "presses_to_beat_computer": 2
}

Routing: the offensive player's script runs CHECK_COL_TYPE_MAN_OR_COM. A human offense goes to the popcorn check or the man-against-man contest directly. A computer offense against a human defender takes the branch the comment calls unreachable, PAUSE_COLL_CHECK_RECHECK_COLL_TYPE, which points the defender's script at the same check, so the defender then runs it as the human side. "Tie" in the comments is a test of the defender's count against 0 (TAX, BEQ after CMP, which leaves A unchanged), so only 0 against 0 puts both players down; equal counts above 0 go to the defender. The computer player's HP lead never wins outright here.

Cited by: Button mashing, Tecmo Super Bowl

Each side picks one of eight slots. The offense's slot reads a play id (0 to 63) from its playbook, and before the snap the game reads the defense's play from a 64-row table: the row is the offense's play id, and the column is the defense's slot. In all 64 rows, the entry in column id ÷ 8, the play's group, is a defensive play that appears nowhere else in the table, one of 11 such plays (computed from the table by the atlas). The playbook-change screen offers slot k only the plays of group k (ids k × 8 to k × 8 + 7), so for a playbook set there, that column is the slot the offense called. tecmo-super-bowl/play-call

About: Tecmo Super Bowl Play calling

{
 "slots": 8,
 "offensive_plays": 64,
 "table": "64 × 8",
 "guess_only_plays": 11
}

Row r's group column is r ÷ 8 (integer division). On that diagonal the 64 entries use 11 values ($22, $53, $57, $5B, $5F, $63, $67, $8F, $99, $BB, $DA), and none of the 448 entries off it uses any of them. The same 16-byte-name-plus-8 layout gives each offensive play its own version by the defense's slot (L3076-L3084). The atlas hasn't traced how the default playbooks (TEAM_PLAYBOOKS, one nibble per slot) become play ids, so the slot-equals-group reading rests on the playbook-change screen.

Cited by: Play calling, Tecmo Super Bowl

Reactions 128 and 177 are player scripts used only by the 11 guess-only defensive plays (computed by the atlas over bank 4). Reaction 128 waits for the snap, sets the player's running-speed rating to 15, adds 48 to his max speed and 48 to his hitting power, moves, and then loops a runRush command; reaction 177 stands for 30 frames after the snap and then jumps into reaction 128's boosts. Execution 188, one of the 11, gives reactions 128 to 134 to its first seven players. The script command the disassembly's macro calls boostRS emits $E3, which the command table maps to the routine that adds to max speed. tecmo-super-bowl/guess-boost

About: Tecmo Super Bowl Play calling

{
 "set_rs_step": 15,
 "max_speed_add": 48,
 "hp_add": 48
}

The scripts found only in guess-only plays are reactions 128 to 138, 160 to 163, 177 to 182, 208, 255 to 257, 294 to 297, 368 to 371, and 452 (computed over bank 4's 255 executions). Not all of them boost: 294 to 297 and 368 to 371 cover receivers. 48 more max speed is three times the MS table's whole range of 16; 48 more HP is 12 rating steps. setRS also resets the current speed from the RS table (L3198-L3203), so the boosted defender starts at 29. The other guess-only scripts vary and aren't claimed here: reaction 129 adds 32 HP instead of 48, and 178, which jumps into it, does too; some, such as 180, end in the passRush loop of reaction 194 rather than 191. Bank 4's labels count from 1, so play index $BB (187) is DEFENSIVE_EXECUTION_188. The stand $1E wait is 30 frames; the data's own annotation reads "for 1.5s".

Cited by: Play calling, Tecmo Super Bowl

When a pass reaches its target, Tecmo Super Bowl adds the passer's pass control (PC) value, 61 to 91 at 2 per step, to the receiver's reception (REC) value, also 61 to 91. With no defender near the ball, a random byte forced into 128–255, times that sum and divided by 256, gives a roll from half the sum to one less than it; 79 or more is a catch, and less is incomplete. Each of up to three nearby defenders in turn subtracts his interception (INT) value, 51 to 81, from the sum (floored at 0) for a roll made the same way: under 51 is an interception, under 80 is incomplete, and 80 or more passes the ball to the next defender's check. A pass that clears every check is a catch. tecmo-super-bowl/pass-outcome

About: Tecmo Super Bowl Pass completion

{
 "pc": [
  61,
  91
 ],
 "rec": [
  61,
  91
 ],
 "int": [
  51,
  81
 ],
 "uncovered_catch_at": 79,
 "interception_below": 51,
 "covered_catch_at": 80
}

The multiply shifts the product's high byte into LOCAL_8 (pc_rec_int_result, qb_to_wr_check_value), so the roll is floor(r × X ÷ 256) with r from 128 to 255. Worked example (computed): PC and REC both 50 on the display scale (step 7, 75 each) against INT 50 (65) give X = 85 and rolls from 42 to 84. A computer team facing a human one adds its season boosts to PC, REC, and INT steps, clamped at 15 (L5688-L5697, L5726-L5738). The comment on MAKES ALWAYS AN INT holds only for a roll of 0, which a sum floored at 0 gives.

Cited by: Pass completion, Tecmo Super Bowl

When the target isn't close enough to the ball, nearby defenders can still intercept: each in turn subtracts his INT value from the variable the code names PASS_CONTROL_VALUE and rolls as for a covered pass, intercepting under 14; otherwise the pass is incomplete. This path doesn't call ADD_PASS_CONTROL_SKILL_AND_REC_SKILL, the routine that stores the passer's value in that variable (the close-target and the jump-or-dive paths call it), so it uses whatever player-command argument was last stored there. The disassembly marks it "***MAJOR BUG!!". tecmo-super-bowl/pass-bug

About: Tecmo Super Bowl Pass completion

{
 "interception_below": 14
}

PLAYER_COMMAND_ARG1 is the argument byte of the last play-script command (for example the new RS step of setRS, L3129), so the value varies with whatever scripts ran before the throw. The atlas hasn't measured how often the path fires.

Cited by: Pass completion, Tecmo Super Bowl

A computer-controlled defense picks its slot at random, 0 to 7, except on third and fourth down. There, with under 25 eighths of a yard to the first-down line (3 yards or less), it calls a run slot (0–3) when a sum of random bytes is under 205 (computed: 80%) and a pass slot (4–7) otherwise. As the atlas reads it, the check meant to favor passes on longer yardage compares the distance's high byte with 57 ($39), and that byte is at most 3 on a 100-yard field, so every longer third or fourth down also gets a random slot. tecmo-super-bowl/com-defense-call

About: Tecmo Super Bowl Play calling

{
 "run_slots": [
  0,
  3
 ],
 "pass_slots": [
  4,
  7
 ],
 "short_yardage_run_chance": "205/256"
}

$50 is 10 yards (Bank20 L1925), so a yard is 8 units, and the goal lines $0670 and $0990 lie 800 units (100 yards) apart. The distance is clamped at the goal line (L1930-L1938), so its high byte is 0 to 3. After the 16-bit compare with $19, A holds that high byte (less a borrow), and CMP #$39 always branches to the random call. The disassembly's comments don't mark this as a bug; the reading is the atlas's. The computer offense makes the same split with the IF_YARDS_TO_GO_LESS_THAN_EQUAL_TO macro and does reach DO_HEAVY_PASS_80PCT_COM_PLAY_CALL (L3680-L3683).

Cited by: Play calling, Tecmo Super Bowl