Castlevania II - Belmont's Revenge:ROM map
Format for PRG-ROM is Bank:RAM address.
(r:symbol) marks the start of a callable subroutine. (RSTxy:symbol) marks a callable subroutine which can be called with the special quick-access RST commands. (t:symbol) marks the start of a data table.
X:7FFF all swappable banks store list their bank number as the last byte of the bank. 0:0000 (RST00:jumptable_entity_state) jumptable (indirect jump by entry in table following call to RST00 according to current entity's state variable) 0:0003 (r:jumptable) jumptable by A. 0:0008 (RST08:ld_from_table) hl <- (hl + 2a) 0:000C (r:ld_hl_hl) hl <- (hl) 0:0010 (RST10:entity_set_image) sets entity's image (see "Images" section below) 0:0018 (RST18:entity_set_timer) sets entity property $08 to A. This seems to be the entity's timer, such as how long until fire despawns or belmont's hitstun. 0:0028 (RST28:add_hl_a) hl += a, then a <- l. 0:0030 (RST30:entity_inc_state) increments the state variable (D:01) of the current entity. 0:0038 (RST38:entity_get_y) get Y position of current entity. 0:01D9 (r:longcall_2_438D) stores current bank (read from $7FFF) on stack, calls routine 2:438D, then returns to caller bank. 0:0D23 (r:entity_set_state_and_substate) entity state <- b, substate (attacking) <- c 0:297B (r:leftshift_bc_4) leftshifts bc by 4. 0:2986 (r:lda_00) a <- $00 0:2989 (r:lda_06) a <- $06 0:298C (r:lda_7F) a <- $7F 0:298F (r:lda_06) a <- $80 0:2AC7 (r:wait_for_blank) Seems to wait to the end of the current blanking period (if applicable) and then to the start of the next. 0:35A9 (r:mbc_bankswap_1) loads swappable bank 1. 0:35AA (r:mbc_bankswap) loads swappable bank from cpu register a. 0:35AF (r:mbc_bankswap_2) loads swappable bank 2. 0:35B5 (r:mbc_bankswap_6) loads swappable bank 6. 0:35BB (r:mbc_bankswap_7) loads swappable bank 7. 0:35C1 (r:mbc_bankswap_3) loads swappable bank 3. 0:38E0 (r:entity_set_animation) Set animation (prop 0C,0B,0A) to (bc):0:(bc+1) (bc):0:(bc+1) 0:3DAC (r:entity_set_x_velocity_0) Entity x velocity <- 00. 0:3DAF (r:entity_set_x_velocity) Entity x velocity <- cb. 0:3DB4 (r:entity_set_y_velocity_0) Entity y velocity <- 00. 0:3DB7 (r:entity_set_y_velocity) Entity y velocity <- cb. 0:3DBA (r:write_word) (hl) <- cb 0:3DBE (r:entity_get_x_velocity) cb <- Entity x velocity. 0:3DC5 (r:entity_get_y_velocity) cb <- Entity x velocity. 0:3DC8 (r:read_word) cb <- (hl) 3:5242 (t:stage_table) (indexed by 0xC8C0, current stage) 3:2868 (r:load_substage) hl <- pointer to table unique to the current substage. 6:421D (r:entity_update) Belmont frame update routine. Called from 0:05FA. 6:4235-4241 Belmont update jumptable 6:427F Belmont state 0 (standing) routine 6:4289 Belmont state 2 (crouching) routine 6:42E9 Belmont state 1 (walking) routine 6:4293 Belmont state 3 (jumping) routine 6:42A1 Belmont state 4 (??) routine 6:44A6 Belmont state 5 (??) routine 6:44D2 Belmont state 6 (??) routine 6:4510 Belmont state 7 (??) routine 6:461B (r:input_A_pressed) A gets zero or 10 depending on if the A button was pressed this frame. Status flags set 6:4621 (r:input_up_down_held) A and status flags 6:4627 (r:input_left_right_held) A and status flags 6:462D (r:input_B_pressed) A and status flags 6:4633 (r:input_B_held) A and status flags 6:4639 (r:input_down_held) A and status flags 6:464B (r:input_up_held) A and status flags 6:4651 (r:input_any_held) A and status flags 6:4801 (r:belmont_set_walk) Read left/right input and set Belmont to be walking left or right accordingly. 6:4817 (r:entity_move_face_right) Entity moves and faces right at velocity 0x90 6:4817 (r:entity_move_face_left) Entity moves and faces left at velocity -0x90
Bank swap routines:
- All are in bank 0, and all write to $2180 to change the bank. For some reason, bank 5 is always swapped inline rather than by function call.
Images - Entities' images are stored in property 0A. Editing this value will change the entity's image -- for example, the axe might appear as a torch, at least until the axe's animation restores the image to the next frame of axe animation. Below is a partially-complete table of images (Please contribute!).
0: Torch (frame 0) 1: Torch (frame 1) 2: Coin (frame 0) 3: Coin (frame 1) 4: Score Orb 5: Small heart 6: Large Heart 7: Wall meat 08: fire (frame 0) 09: fire (frame 1) 0A: 1-up 0B: holy water (icon) 0C: holy water (projectile) 0D-10: Axe/Cross (frames 0-3) 11-23: Belmont poses 24-29: whip
and so on.