Toshiba TMPR7901, User Manual

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Chapter 12: 10/100 IEEE802.3 Media Access Controller
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
12-33
12.3.3 MIIM (Media Independent Interface Management)
12.3.3.1 MIIM Control Register
The MIIM control register allows the C790 to read and write any one of the PHYs connected
to the MAC. This register provides bits to address a particular PHY, to address a register, to
set the read or write direction, and to indicate that the read or write is still in progress. Upon
the completion of reset, this register’s value is 0x0000_0000.
63 32
0
32
31 16 15 11 10 6 5 2 1 0
0
PA
REG 0
Wri
te
Bu
sy
16 5 5 4 1 1
Figure 12-3 Fields of MIIM Control Register
Table 12-31 MIIM Control Register Field Descriptions
Bit(s) Field Description
15:11 PA[4:0]
PHY Address
The 5-bit address of the PHY being read or written
10:6 REG[4:0]
Register Address
The 5-bit address of the MIIM register being read or written
5:2 - Reserved
1 Write
MIIM Write
When set, indicates that this is a write operation on the PHY with the data in the MIIM data register
0
Busy
(Read)
MIIM Busy
When set, indicates a MIIM management read or write operation. If the Busy bit is set, writes to the
MIIM Control or Data Register are ignored. The Busy bit should be 0 when writing to these registers.
(Note : The MIIM data register must contain valid transmit data prior to writing to this MIIM Control
Register)