MOTOROLA
Chapter 17. Fast Ethernet Controller (FEC)
17-31
Programming Model
If the MMFR register is written while frame generation is in progress, the frame contents
will be altered. Software should use the MII_STATUS register and/or the MII interrupt to
avoid writing to the MMFR register while frame generation is in progress.
17.5.4.7 MII Speed Control Register (MSCR)
The MSCR provides control of the MII clock (EMDC pin) frequency, allows a preamble
drop on the MII management frame, and provides observability (intended for
manufacturing test) of an internal counter used in generating the EMDC clock signal.
The MII_SPEED field must be programmed with a value to provide an EMDC frequency
of less than or equal to 2.5 MHz to be compliant with the IEEE 802.3 MII specification.
The MII_SPEED must be set to a non-zero value in order to source a read or write
management frame. After the management frame is complete the MSCR register may
optionally be set to zero to turn off the EMDC. The EMDC generated will have a 50% duty
cycle except when MII_SPEED is changed during operation (change will take effect
following either a rising or falling edge of EMDC).
31
16
Field
—
Reset
0000_0000_0000_0000
R/W
R/W
15
8
7
6
1
0
Field
—
DIS_PREAMBLE
MII_SPEED
—
Reset
0000_0000_0000_0000
R/W
R/W
Address
0x1044
Figure 17-10. MII Speed Control Register (MSCR)
Table 17-18. MSCR Field Descriptions
Bits
Name
Description
31–8
—
Reserved, should be cleared.
7
DIS_PREAMBLE Asserting this bit will cause preamble (32 1’s) not to be prepended
to the MII management frame. The MII standard allows the preamble
to be dropped if the attached PHY device(s) does not require it.
6–1
MII_SPEED
MII_SPEED controls the frequency of the MII management interface
clock (EMDC) relative to the system clock. A value of 0 in this field
will “turn off” the EMDC and leave it in low voltage state. Any
non-zero value will result in the EMDC frequency of
1/(MII_SPEED*2) of the system clock frequency.
0
—
Reserved, should be cleared.
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...