Freescale Semiconductor MC68HC08KH12 - Manual (Page 115)

MC68HC(7)08KH12 — Rev. 1.1 Advance Information
Freescale Semiconductor 115
Features of the embedded device function include the following:
• Device Control Endpoint 0 and Interrupt Endpoints 1 and 2
– 8-byte transmit buffer
– 8-byte receive buffer
• Device Interrupt Endpoints 1 and 2
– 8-byte transmit buffer
• USB generated interrupts
– transaction interrupt driven
9.3 Overview
This section provides an overview of the Universal Serial Bus (USB)
module developed for the MC68HC(7)08KH12. This USB module is
designed to serve as a compound device, and operates from a reference
frequency of 48MHz, derived from the CGM
(see Section 8. Clock
Generator Module (CGM) ). An embedded full speed device function is
combined with a hub in a single USB module. For the hub sub-module,
five basic properties can be supported by the hardware or the software:
connectivity behavior, power management, device connect/disconnect
detection, bus fault detection and recovery, and full/low speed device
traffic control. Endpoint 0 of the hub sub-module functions as a
receive/transmit control endpoint. Endpoint 1 of the hub sub-module
functions as interrupt transfer to report the device change state. For the
embedded device sub-module, three types of USB data transfers are
supported: control, interrupt, and bulk (transmit only). Endpoint 0 of the
embedded device sub-module functions as a receive/transmit control
endpoint. Endpoints 1 and 2 of the embedded device sub-module can
function as interrupt or bulk, but only in the transmit direction.
A block diagram of the USB module is shown Figure 9-1 . The USB
module manages communications between the host and the USB
function. The module is partitioned into eight functional blocks. These
blocks consist of a 3.3 volt regulator, a dual function transceiver, the hub
repeater function, the SIE (Serial Interface Engine), the frame counter
logic, the hub control logic, the embedded device control logic, and the
endpoint registers.