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Ethernet Module
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
11-31
11.5.20 Pointer-to-Transmit Descriptor Ring (ETDSR)
This register provides a pointer to the start of the circular transmit buffer descriptor queue in external
memory. This pointer must be long-word aligned. However, it is recommended it be aligned on a 16 byte
boundary (address evenly divisible by 16) in order to improve bus utilization. Bits 1 and 0 should be set
to 0 by the user. Non-zero values in these two bit positions are ignored by the hardware.
This register is not reset and must be initialized by the user prior to operation.
31
16
Field
X_DES_START
Reset
Undefined
R/W
Read/Write
15
2
1
0
Field
X_DES_START
0
0
Reset
Undefined
R/W
Read/Write
Addr
MBAR + 0xC14
Figure 11-25. Pointer-to-Transmit Descriptor Ring (ETDSR)
Table 11-28. ETDSR Field Descriptions
Bits
Name
Description
31–2
X_DES_START
Pointer to start of transmit buffer descriptor queue.
1–0
—
Reserved, should be cleared.