NXP Semiconductors LPC24XX UM10237 - Manual (Page 225)

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User manual Rev. 04 — 26 August 2009 225 of 792
NXP Semiconductors
UM10237
Chapter 11: LPC24XX Ethernet
7.1.9 MII Mgmt Configuration Register (MCFG - 0xFFE0 0020)
The MII Mgmt Configuration register (MCFG) has an address of 0xFFE0 0020. The bit
definition of this register is shown in
Table 11–196 .
7.1.10 MII Mgmt Command Register (MCMD - 0xFFE0 0024)
The MII Mgmt Command register (MCMD) has an address of 0xFFE0 0024. The bit
definition of this register is shown in
Table 11–198 .
Table 195. Test register (TEST - address 0xFFE0 ) bit description
Bit Symbol Function Reset
value
0 SHORTCUT PAUSE
QUANTA This bit reduces the effective PAUSE quanta from 64 byte-times to 1 byte-time. 0
1 TEST PAUSE This bit causes the MAC Control sublayer to inhibit transmissions, just as if a
PAUSE Receive Control frame with a nonzero pause time parameter was received. 0
2 TEST
BACKPRESSURE Setting this bit will cause the MAC to assert backpressure on the link. Backpressure
causes preamble to be transmitted, raising carrier sense. A transmit packet from the
system will be sent during backpressure. 0
31:3 - Unused 0x0
Table 196. MII Mgmt Configuration register (MCFG - address 0xFFE0 0020) bit description
Bit Symbol Function Reset
value
0 SCAN INCREMENT Set this bit to cause the MII Management hardware to perform read cycles across a
range of PHYs. When set, the MII Management hardware will perform read cycles
from address 1 through the value set in PHY ADDRESS[4:0]. Clear this bit to allow
continuous reads of the same PHY. 0
1 SUPPRESS
PREAMBLE Set this bit to cause the MII Management hardware to perform read/write cycles
without the 32 bit preamble field. Clear this bit to cause normal cycles to be
performed. Some PHYs support suppressed preamble. 0
4:2 CLOCK SELECT This field is used by the clock divide logic in creating the MII Management Clock
(MDC) which IEEE 802.3u defines to be no faster than 2.5 MHz. Some PHYs
support clock rates up to 12.5 MHz, however. Refer to
Table 11–197 below for the
definition of values for this field.
0
14:5 - Unused 0x0
15 RESET MII MGMT This bit resets the MII Management hardware. 0
31:16 - Unused 0x0
Table 197. Clock select encoding
Clock Select Bit 4 Bit 3 Bit 2
Host Clock divided by 4 0 0 x
Host Clock divided by 6 0 1 0
Host Clock divided by 8 0 1 1
Host Clock divided by 10 1 0 0
Host Clock divided by 14 1 0 1
Host Clock divided by 20 1 1 0
Host Clock divided by 28 1 1 1