Nuts and Volts - December 2008

the UART, SPI, and FIFO interfaces make up what is termed the combined interface.

There are currently six precompiled Vinculum supervisory firmware versions:

• VDIF

• VMSC

• VDPS

• VCDC

• VDFC

Disk and FTDI interface
Music player
Disk, PC monitor, and slave port
Communication class device
Disk and file copier

• VDAP

Disk and peripherals

My VDIP2 is loaded with VDAP, the general-purpose firmware loads and supports USB devices on USB ports 1 and 2 with the exception of the USB BOMS device, which is only supported on USB port 2. The VDAP command monitor communicates with the monitor device using one of the interfaces that make up the combined interface.

The VNC1L’s command monitor operates in two modes. Data mode is used to pass information from the command monitor directly to another device on USB port 1 or USB port 2. To communicate with the VNC1L’s command interpreter, Command Mode must be invoked. The DATAACK# and DATAREQ# pins (the # means that the pin is active low) are used to switch between Data Mode and Command Mode.

The VNC1L firmware will start in Command Mode. The DATAACK# and DATAREQ# pins need to be held logically high at firmware start to assure

■ SCHEMATIC 1. Looks very similar to an everyday USB-enabled microcontroller circuit, doesn’t it? Well, it is... sorta. However, we don’t have to write a single byte of supervisor code. Several different FTDI-supplied, application-specific firmware images can be loaded into the VNC1L. All we need to do is to integrate a PICinto this picture.