11-26
MCF5272 User’s Manual
Programming Model
11.5.16 RAM Perfect Match Address Low (ADDR_LOW)
The ADDR_LOW register contains the lower 32 bits of the 48 bit MAC address used in the
address recognition process to compare with the Destination Address field of the receive
frames.
This register, shown in Figure 11-19, is not reset and must be initialized by the user prior
to operation.
11.5.16.1 RAM Perfect Match Address High (ADDR_HIGH)
The ADDR_HIGH register contains bytes 4 and 5 of the 48-bit MAC address used in the
address recognition process to compare with the destination address field of the receive
frames. Byte 0 is the first byte transmitted on the network at the start of the frame.
This register is not reset and must be initialized by the user prior to operation. See
1
HBC
Heartbeat control. If set, the heartbeat check is performed following end of transmission and
the HB bit in the status register is set if the collision input does not assert within the heartbeat
window. This bit should be modified only when ETHER_EN is deasserted.
0
GTS
Graceful transmit stop. When this bit is set, the MAC stops transmission after any current
frame is complete and the GRA interrupt in the INTR_EVENT register is asserted. If frame
transmission is not currently underway, the GRA interrupt is asserted immediately. Once
transmission is complete, a restart is accomplished by clearing the GTS bit. The next frame in
the transmit FIFO is then transmitted. If an early collision occurs during transmission when
GTS = 1, transmission stops after the collision. The frame is transmitted again once GTS is
cleared. Note that there may be old frames in the transmit FIFO that are transmitted when
GTS is reasserted. To avoid this, deassert ETHER_EN following the GRA interrupt.
31
16
Field
ADDR_LOW
Reset
Undefined
R/W
Read/Write
15
0
Field
ADDR_LOW
Reset
Undefined
R/W
Read/Write
Addr
MBAR + 0xC00
Figure 11-19. RAM Perfect Match Address Low (ADDR_LOW)
Table 11-23. ADDR_LOW Field Descriptions
Bits
Name
Description
31–0
ADDR_LOW
Bytes 0 (bits 31–24), 1 (bits 23–16), 2 (bits 15:8), and 3 (bits 7–0) of the 6-byte address.
Table 11-22. X_CNTRL Field Descriptions (Continued)
Bits
Name
Description
Содержание DigitalDNA ColdFire MCF5272
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