Writing Scripts
Each line in a script file is one command. There is no provision for extending lines beyond one line. A line
is terminated by a carriage return.
The first character of a line is the command. Commands are:
I Set interface bus to use
r Read from the serial control bus
w Write to the serial control bus
# Comment
b Break
d Delay
The first command, I, sets the interface to use for the commands to follow. This command must be
followed by one of the following parameters:
i2cstd Standard mode I
2
C Bus
i2cfast Fast mode I
2
C bus
spi8 SPI bus with 8-bit register addressing
spi16 SPI bus with 16-bit register addressing
gpio Use the USB-MODEVM GPIO capability
For example, if a fast mode I
2
C bus is to be used, the script would begin with:
I i2cfast
No data follows the break command. Anything following a comment command is ignored by the parser,
provided that it is on the same line. The delay command allows the user to specify a time, in milliseconds,
that the script will pause before proceeding.
Note: UNLIKE ALL OTHER NUMBERS USED IN THE SCRIPT COMMANDS, THE DELAY
TIME IS ENTERED IN A DECIMAL FORMAT. Also, note that because of latency in the
USB bus as well as the time it takes the processor on the USB-MODEVM to handle
requests, the delay time may not be precise.
A series of byte values follows either a read or write command. Each byte value is expressed in
hexadecimal, and each byte must be separated by a space. Commands are interpreted and sent to the
TAS1020 by the program using the protocol described in Section G.1 .
The first byte following a read or write command is the I
2
C slave address of the device (if I
2
C is used) or
the first data byte to write (if SPI is used—note that SPI interfaces are not standardized on protocols, so
the meaning of this byte will vary with the device being addressed on the SPI bus). The second byte is the
starting register address that data will be written to (again, with I
2
C; SPI varies—see Section G.1 for
additional information about what variations may be necessary for a particular SPI mode). Following these
two bytes are data, if writing; if reading, the third byte value is the number of bytes to read, (expressed in
hexadecimal).
For example, to write the values 0xAA 0x55 to an I
2
C device with a slave address of 0x90, starting at a
register address of 0x03, one would write:
#example script
I i2cfast
w 90 03 AA 55
r 90 03 2
This script begins with a comment, specifies that a fast I
2
C bus will be used, then writes 0xAA 0x55 to the
I
2
C slave device at address 0x90, writing the values into registers 0x03 and 0x04. The script then reads
back two bytes from the same device starting at register address 0x03. Note that the slave device value
does not change. It is not necessary to set the R/ W bit for I
2
C devices in the script; the read or write
commands will do that.
SLAU218 – August 2007 USB-MODEVM Protocol 53
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