HC08 Full Chip Simulation
Configuration Procedure
309
Microcontrollers Debugger Manual
Syntax
>INPUTS
Example
>INPUTS
Show I/O port input values.
FCS Universal Serial Bus (USB) Module
Some of the microcontrollers in the MC68HC08 family contain USB compliant peripheral
devices. These can be low-speed or high-speed USB slave devices. This means that all
USB transfers are initiated by a host (i.e. a personal computer) and that the microcontroller
needs to be setup to respond with the appropriate acknowledgement messages. According
to the USB specification, there are a series of messages that go back and forth between the
host and the device in order to setup and describe the channel for data transfer. All of these
messages can be set up through the USB I/O commands built into the full chip simulator.
This FCS mode simulates all functionality of the Universal Serial Bus (USB) module
including:
• Flag polling
• Interrupt enabled mode
• Transmission and reception of external data
• Endpoint 0/1/2 modes of operation
• USB reset functionality
• STALL, NAK and ACK handshakes
This section goes through an example of assembly code, showing how the simulator can
be used to test out code for driving the USB peripheral.
Listing 11.2 shows an assembly program that exercises the USB full speed peripheral on
the 68HC908JW32. The source assembly file can be downloaded from the P&E
Microcomputer website at www.pemicro.com. With minor modifications this assembly
file can be added and compiled as a part of your Freescale project. It sets the
microcontroller up as a simple USB human interface device (HID) and uses interrupts
from the USB peripheral to service requests from the host. This code can be assembled
and then loaded into the ICS08 simulator for execution, after which simulator commands
can be used to emulate the USB packets that come from the host. Let us first break down
what is being done in the example program.
Listing 11.2 68HC908JW32 USB HID Demonstration Application
; 68HC908JW32 USB HID Demonstration Application