ADAV4601 System Design Document Confidential Information
Rev.1 August 2009 Analog Devices Page 49
READ/WRITE DATA FORMATS
The read/write formats of the control port are designed to be byte oriented. This allows easy programming of
common microcontroller chips. To fit into a byte-oriented format, 0s are appended to the data fields before the MSB
to extend the data-word to eight bits. For example, 28-bit words written to the parameter RAM are appended with
four leading 0s to equal 32 bits (4 bytes); 40-bit words written to the program RAM are not appended with 0s
because they are already a full five bytes. These zero-padded data fields are appended to a 3-byte field consisting of
a 7-bit chip address, a read/write bit, and an 16-bit RAM/register address. The control port knows how many data
bytes to expect based on the address given in the first three bytes.
The total number of bytes for a single location write command can vary from five bytes (for a control register write)
to eight bytes (for a program RAM write). Burst mode can be used to fill contiguous register or RAM locations. A
burst mode write begins by writing the address and data of the first RAM or register location to be written to.
Rather than ending the control port transaction (by issuing a stop command in I
2
C mode), as would be done in a
single-address write, the next data-word can be written immediately without specifying its address.
To Next Page
Loading...
Need help?
General
