User Manual

Host Interface
Rev 1.2 Apr-05 Proprietary and confidential 29
Host Interface
This chapter provides detailed information about the Host-EM interface,
describing the signals required for serial data transfer, handshaking and digital
module I/O (MIO).
Operation modes
The embedded module supports the following logical communication interfaces:
• Data channel—Supports AT command and PPP packet exchange during
data calls
• Control channel—Supports modem control and call processing commands
• Diagnostic channel – Supports modem status and diagnostic logging
USB interface
The USB physical interface is the only path for communication between the host
and modem.
General USB background information can be found in the Compaq, Intel,
Microsoft, and NEC Universal Serial Bus Specification.
The USB interface is designed to comply with the Universal Serial Bus
Specification, Revision 1.1. The EM USB interface supports the full-speed
(12 Mbps) data rate, and can be used to transfer general data, phone diagnostic
data, over-the-air data, or voice PCM samples between the module and a USB
host. The USB interface provides 10 endpoints:
• One bi-directional control endpoint
• Isochronous IN and OUT endpoints for voice
• Four IN endpoints
• Three OUT endpoints
For more background information on USB, see the Compaq, Intel, Microsoft, and
NEC Universal Serial Bus Specification.