Technical data

Firmware Description
USB and PS/2 Multimedia Keyboard Interface, Rev. 1
Freescale Semiconductor 11
1.5 Firmware Description
The firmware consists of three main parts:
• USB and PS/2 interface detection
• PS/2 main program and subroutines
• USB main program and subroutines
DELAY 350ms (POWER ON DELAY)
INITIALIZATION
ENABLE USB D– PULLUP
D+ HIGH FOR 1ms ?
OVER 10 SECONDS ?
USB RESET?
D+ HIGH FOR 1ms ?
NO
NO
NO
YES
SETUP DETECTED ?
NO
OVER 10 SECONDS ?
NO
NO
PS/2
USB
PS/2
USB
USB
YES
YES
YES
YES
YES
Figure 1-7. USB and PS/2 Detection