jetpac: Routine at 6e66

6e66: Reads 2 bytes of pixel data from a sprite.

Used by the routine at 6ea5.

Input
B	Loop counter - sprite height?
HL	Address of byte for current sprite.

Output
B	Same value as on entry.
D	First byte of pixel data.
E	????
C	Second byte of pixel data.
HL	Address to the next byte of the sprite.

6e66

ld a,b

Backup B value

6e67

ex af,af'

6e68

ld e,$00

E=third byte - NULL on read

6e6a

ld c,(hl)

C=first pixel byte

6e6b

inc hl

6e6c

ld d,(hl)

D=second pixel byte

6e6d

inc hl

Set HL to next byte (used later)

6e6e

ld a,b

Return if B == 0

6e6f

and a

6e70

ret z

Rotating the bits.

6e71

srl c

Executes B times

6e73

rr d

6e75

rr e

6e77

djnz $6e71

6e79

ex af,af'

Restore B to the entry value

6e7a

ld b,a

6e7b

ret