------------------------ D7 D6 D5 D4 D3 D2 D1 D0 (The D0 bit (LSB) is sent first) ------------------------ (1) YV XV YS XS 1 M R L (overflow, sign, buttons) (2) X7 X6 X5 X4 X3 X2 X1 X0 (X movement; -128 to +127) (3) Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 (Y movement; -128 to +127) (4) Z7 Z6 Z5 Z4 Z3 Z2 Z1 Z0 (Z movement; -128 to +127) M = Middle Button State (1 = pressed down) L = Left Button State (1 = pressed down) R = Right Button State (1 = pressed down) XS = Direction of X movement (1 = LEFT) YS = Direction of Y movement (1 = UP) XV = Overflow of X movement value (1 = X overflow occured) YV = Overflow of Y movement value (1 = Y overflow occured) X7,...,X0 : X movement; 8-bit 2's-complement signed byte (-128 to +127) Y7,...,Y0 : Y movement; 8-bit 2's-complement signed byte (-128 to +127) Z7,...,Z0 : Mouse wheel movement; 8-bit 2's-complement signed byte (The Z value is forced to a range of -8 to +7)