Programming Model

Field

Reset

R/W

Field

Reset

R/W Address

31

16

R_DES_START

Uninitialized

R/W

15

2

1

0

R_DES_START

Uninitialized

R/W

IPSBAR + 0x1180

Figure 17-24. Receive Descriptor Ring Start Register (ERDSR)

Table 17-33. ERDSR Field Descriptions

Bits

Name

Descriptions

 

 

 

31–2

R_DES_START

Pointer to start of receive buffer descriptor queue.

 

 

 

1–0

Reserved, should be cleared.

 

 

 

17.5.4.22 Transmit Buffer Descriptor Ring Start (ETSDR)

The ETSDR is written by the user. It provides a pointer to the start of the circular transmit buffer descriptor queue in external memory. This pointer must be 32-bit aligned; however, it is recommended it be made 128-bit aligned (evenly divisible by 16). Bits 1 and 0 should be written 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.

Field

Reset

R/W

Field

Reset

R/W Address

31

16

X_DES_START

Uninitialized

R/W

15

2

1

0

X_DES_START

Uninitialized

R/W

IPSBAR + 0x1184

Figure 17-25. Transmit Buffer Descriptor Ring Start Register (ETDSR)

MOTOROLA

Chapter 17. Fast Ethernet Controller (FEC)

17-43

Page 399
Image 399
Motorola MCF5281, MCF5282 user manual Transmit Buffer Descriptor Ring Start Etsdr, Rdesstart, Xdesstart