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Routines |
| Prev: F289 | Up: Map | Next: F2F9 |
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Used by the routine at F350.
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| F296 | CALL $F274 | Pick a code sheet reference for the code that the player has to enter | ||
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This entry point is used by the routine at F350.
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| F299 | CALL $0D6B | Clear the screen (ROM CLS routine) | ||
| F29C | LD A,$02 | Stream type = 2 | ||
| F29E | CALL $1601 | Open stream for printing | ||
| F2A1 | LD BC,$111B | B = character row (27), C = column (17) | ||
| F2A4 | CALL $0DD9 | These values are reversed and used to calculate screen address position in HL (16614) ready to print at. | ||
| F2A7 | CALL $F268 | Print the following characters/message on screen. Return from CALL goes to instructions after the message, at F2BD |
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Initial screen message text:
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| F2AA | DEFM "Type in number at " | Message to be printed (at previous CALL) | ||
| F2BC | DEFB $FF | End-of-string marker | ||
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Print the co-ordinates for the required code from the code sheet.
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| F2BD | LD A,($F261) | Value (0-16) signifying first part of code that the player needs to enter | ||
| F2C0 | ADD A,$41 | 65 added to this code, to give it values of between 65 and 80 This corresponds to ASCII character codes (A to P) |
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| F2C2 | RST $10 | Print this value on screen | ||
| F2C3 | LD A,$2C | ASCII value for comma (,) | ||
| F2C5 | RST $10 | Print it | ||
| F2C6 | LD A,($F260) | Get the second part of the code (number from 0-41) | ||
| F2C9 | CP $0A | Is it <10? | ||
| F2CB | JR C,$F2EF | If so, fine to go ahead and print it as it's only 1 character (0-9) | ||
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Code number value is >=10 so we'll need to print two numeric characters
The next routine identifies the first digit (D register) as 49, 50, 51 or 52 - ASCII codes for 1, 2, 3 or 4 - for the 10s digit
Then prints that followed by the following value. |
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| F2CD | LD D,$31 | ASCII value for '1' - first digit | ||
| F2CF | LD E,$0A | Offset value for 2nd digit | ||
| F2D1 | CP $14 | Code number <20? | ||
| F2D3 | JR C,$F2E9 | |||
| F2D5 | LD D,$32 | If not, set ASCII value for '2' - first digit | ||
| F2D7 | LD E,$14 | Offset value for 2nd digit | ||
| F2D9 | CP $1E | Code number <30? | ||
| F2DB | JR C,$F2E9 | |||
| F2DD | LD D,$33 | If not, set ASCII value for '3' - first digit | ||
| F2DF | LD E,$1E | Offset value for 2nd digit | ||
| F2E1 | CP $28 | Code number <40? | ||
| F2E3 | JR C,$F2E9 | |||
| F2E5 | LD D,$34 | If not, set ASCII value for '4' - first digit | ||
| F2E7 | LD E,$28 | Offset value for 2nd digit | ||
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Print the first digit (tens) of the code:
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| F2E9 | LD A,D | Get the ASCII code value | ||
| F2EA | RST $10 | Print the first code digit | ||
| F2EB | LD A,($F260) | As it's two digits, we need to get the second | ||
| F2EE | SUB E | So subtract the offset (the 'tens' amount) from its value (e.g. 25-20 to get 5) | ||
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Print the second digit (ones) of the code:
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| F2EF | ADD A,$30 | Add 48 to get to ASCII values for characters 0 to 9 (48-57) | ||
| F2F1 | RST $10 | Print the second code digit | ||
| F2F2 | CALL $F1FA | Retrieve the code from the code table at ECB8 2 byte code returned in DE (first - low - byte in E, second - high - byte in D) |
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| F2F5 | LD ($F1F8),DE | Store the code in a 2-byte holding buffer | ||
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