Cirrus Logic CobraNet - Manual (Page 30)

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Copyright 2006 Cirrus Logic, Inc. DS651PM25
CobraNet Programmer’s Reference
Management Interface Variable Reference
6.2.4 PhysAddress
A 48-bit Ethernet media access control (MAC) address.
24-bit HMI: Data is stored in the most-significant 16 bits of 3 consecutive memory
locations as illustrated below. The least-significant 8 bits of each location are read as zero
and
must be written as zero.
32-bit HMI: Data is stored in two consecutive words as shown below. A third word is
unused and reserved for addressing compatibility with 24-bit platforms.
6.2.5 TimeTicks
TimeTicks is an integer encoding for time durations in units of 100ths of a second.
24-bit HMI: An unsigned timer value is available in two successive 24-bit words. A 32-bit
timer value and 15-bit fractional extension are available as shown below. The fractional
extension may be used to gain additional accuracy. It may be safely ignored for most
applications.
32-bit HMI: TimeTicks value is available as two sucessive 32-bit words. A 32-bit timer
value, a 16-bit rollover, and 16-bit fractional extension are availabe as shown below. The
fractional extension may be used to gain additional accuracy. The rollover extension may
Table 12. MAC address Layout, 24-bit Platforms
MS Middle LS
Word 1 MAC byte 2 MAC byte 1 0
Word 2 MAC byte 4 MAC byte 3 0
Word 3 MAC byte 6 MAC byte 5 0
Table 13. MAC address Layout, 32-bit Platforms
MS MH ML LS
Word 1 MAC byte 2 MAC byte 1 MAC byte 4 MAC byte 3
Word 2 MAC byte 6 MAC byte 5 unused unused
Word 3 unused unused unused unused
Table 14. TimeTicks Layout, 24-bit Platforms
MS Middle LS
Word 1 Timer MS Timer MH Timer ML
Word 2 Timer LS Fractional LS Fractional MS