Avalon: Routine at F350

F350: Code sheet - code entry count and validation

Input
B	3 - number of correct responses needed (set in previous routine)

Keeps count of correct and incorrect codes entered, displaying a message if a wrong code is entered.

THREE correct codes need to be entered to start the game proper
ONE incorrect code is allowed, the machine is reset upon the second incorrent entry

F350

PUSH BC

Store number of codes left to enter

F351

CALL $F296

Set up player code entry

RET from F34A after code that has been input is compared with valid code.

Zero flag set (Z) indicates there's a match - the code is correct.
Non-zero (NZ) indicates the wrong code has been entered.

F354

JR Z,$F393

Jump out here if correct code entered

F356

CALL $F268

Print the following 'wrong code' message text on screen.
Jump down to F37C on RETurn after printing

Wrong code message text:

F359

DEFB $0D,$0D

Codes for ENTER x 2 (move two lines down)

F35B

DEFM " That is wrong - one more try"

F37B

DEFB $FF

End-of-message marker

Pause for a few seconds:

F37C

LD DE,$000A

Set outer loop counter (10)

F37F

LD HL,$0000

Set inner loop counter (65536)

Pause loop:

F382

DEC DE

Outer loop - decrement DE counter

F383

DEC HL

Inner loop - decrement HL counter

F384

LD A,H

Has inner loop counter reached zero?

F385

OR L

F386

JR NZ,$F383

If not, continue to decrement inner loop counter

F388

DEC DE

Decrement outer loop counter

F389

LD A,D

Has outer loop counter reached zero?

F38A

OR E

F38B

JR NZ,$F382

If not, continue to decrement both counters

F38D

CALL $F299

Give the player another chance to enter the right code

F390

JP NZ,$0000

...This time if there's no match, reset the computer.

Correct code has been entered

F393

POP BC

Retrieve the number-of-codes-entered counter

F394

DJNZ $F350

Decrement and continue code generation and entry for 3 iterations

F396

JP $BF1A

3 codes have been correctly entered. Jump to initialize the game.