NEC Network Controller uPD98502 - Manual (Page 247)

CHAPTER 4 ATM CELL PROCESSOR
Preliminary User’s Manual S15543EJ1V0UM 247
4.5 Data Structure
ATM Cell Processor has Tx/Rx buffer structure similar to that of Ethernet Controller and USB Controller.
4.5.1 Tx buffer structure
The following figure shows Tx buffer structure used by ATM Cell Processor. It consists of a packet descriptor,
some buffer directories, and data buffers. A Rx buffer structure and a Tx buffer structure are similar, so that
reconstructing buffer structure is not needed when sending out a received packet.
Figure 4-8. Tx Packet
Tx buffer desc.
Tx buffer desc.
Tx buffer desc.
Data
Buffer
Data
Buffer
Tx buffer desc. (L=1)
Data
Buffer
Data
Buffer
Link pointer
Tx buffer desc.
Null pointer
Data
Buffer
Pointer to be send
with Tx_ready
Tx packet descriptor Tx buffer dir.
Tx buffer dir.