Datasheet

4−1
4 Application
4.1 Keyboard Section
Table 4−1 outlines the GPIO assignment for the switch-matrix scanning and for keyboard LED drive. Figure 4−1
illustrates the port-3 pins that are assigned to drive the four keyboard LEDs. As shown, P3[5:2] can sink up to 12 mA
(open-drain output) on each pin. Figure 4−2 illustrates the 18 outputs (open-drain) and the 8 inputs (internal pullups)
that are used for the switch-matrix scanning. Figure 4−3 illustrates the partial connection bus power mode. Figure
4−4 shows the USB upstream connection, and Figure 4−5 illustrates the downstream connection (only one port
shown).
Table 4−1. GPIO Assignment for Matrix Scan and LED Drive
GPIO I/O
P0[7:0] O 8-bit matrix-scan outputs
P1[7:0] O 8-bit matrix-scan outputs
P3.6 O 1-bit matrix-scan output
P3.7 O 1-bit matrix-scan output
P2[7:0] I 8-bit matrix-scan inputs
P3.2 O Keyboard LED-1
P3.3 O Keyboard LED-2
P3.4 O Keyboard LED-3
P3.5 O Keyboard LED-4
P3.0 I/O GPIO (Not used for keyboard)
P3.1 I/O GPIO (Not used for keyboard)
TUSB2136
P3.2
P3.3
P3.4
P3.5
V
CC
Figure 4−1. Keyboard LED Connection