| Routines

7427: Update the SRB for the speech bubble

Used by the routines at 734E (when printing the speech bubble) and 7432 (when removing the speech bubble). Sets the bits in the screen refresh buffer (SRB) that correspond to the speech bubble, so that they are refreshed when the display is updated.
Input
DE | SRB byte address
7427 | LD A,$FF | Set all bits in this SRB byte, indicating that 8 squares in a row (the bottom half of the bubble) need refreshing
7429 | LD (DE),A
742A | LD A,E | Point DE at the SRB byte corresponding to the next row up
742B | SUB $04
742D | LD E,A
742E | LD A,$FF | Set all bits in this SRB byte, indicating that 8 squares in a row (the top half of the bubble) need refreshing
7430 | LD (DE),A
7431 | RET |