Maxim Integrated MAXQ622 - Manual (Page 172)

MAXQ612/MAXQ622 User’s Guide
12-2 Maxim Integrated
SECTION 12: UNIVERSAL SERIAL BUS (USB) INTERFACE
Note: This section only applies to the MAXQ622.
The MAXQ622 provides a USB 2 .0 full-speed interface compliant with the Universal Serial Bus Revision 2 .0
Specification . The full-speed USB transceiver provides a complete USB interface between the MAXQ622 and a host
USB controller . The MAXQ622 internally generates the USB clock from the 12MHz input .
Firmware libraries are available for the MAXQ622 that support the Windows
® standard HID interface for plug-and-play
compatibility without the necessity of loading any drivers on the USB host device (PC) . The USB controller described
in this document is compliant with USB Revision 2 .0 Specification full-speed operation . The USB specification can be
found on www .usb .org .
The USB controller allows the MAXQ-based microcontroller to function as a full-speed USB peripheral device . The
CPU communicates to the USB controller chip through the SFR interface . The MAXQ622 provides a USB serial inter-
face engine (SIE) that, through connection to the internal USB transceiver, allows the microcontroller to function as a
USB 2 .0-compliant full-speed device . The USB SIE on the MAXQ622 implements four endpoints, each with single- or
double-buffered, 64-byte data storage .
12.1 USB SIE Endpoint Description
1) EP0: Mandatory bidirectional control-type endpoint with a single-buffered, 64-byte data buffer
2) EP1: Output bulk- or INT-type endpoint with a double-buffered, 64-byte data buffer
3) EP2: Input bulk- or INT-type endpoint with a double-buffered, 64-byte data buffer
4) EP3: Input bulk- or INT-type endpoint with a single-buffered, 64-byte data buffer
Note that all endpoint directions are from the host standpoint, so an input endpoint writes data out to the host . Double-
buffering EP1 and EP2 improves throughput by allowing the CPU to read or load the next packet while the USB control-
ler is moving the current packet over USB . EP3-IN is intended to serve as a large interrupt endpoint for various USB
class specifications such as the Still Image Capture Device . It can also be used as a second bulk-IN endpoint .
Figure 12-1. MAXQ622 USB Connection
Figure 12-2. USB Interface
Windows is a registered trademark of Microsoft Corp.
MAXQ622
V DD V DDB
V BUS V DDIO
D-
REG18
GND
BATTERY
D+
VBUS
D-
D+
GND
MAXQ
CPU
USB
HOST
USB
CONTROLLER
(FUNCTION)
USB
TRANSCEIVER