MC68HC(7)08KH12Rev. 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.