NEC Network Controller uPD98502 - Manual (Page 262)

CHAPTER 4 ATM CELL PROCESSOR
262 Preliminary User’s Manual S15543EJ1V0UM
4.7.6 Indirect_Access command
The Indirect_Access command is used to perform read/write access to Work RAM.
Figure 4-23. Indirect_Access Command
[Indirect_Access command]
CMR
0 R/W B3 B2 B1 B0 Address 0
31 29 28 27 26 25 24 23 2 1 0
CER
Data
31 0
Indirect_Access command
R/W Specifies whether access to the target is a read or a write access.
1: Read
0: Write
B0, B1, B2, B3 For write access, used to select bytes.
Address If the address specified in this area is within control memory, the virtual address is converted to
ATM Cell Processor address. Otherwise, the address is used as is. The low-order two bits of
the address must be 0, that is, the address must be a word address.
4.8 Operations
In this section, functional specifications mainly SAR function is described.
4.8.1 Work RAM usage
The size of the Work RAM is 16 Kbytes. This memory is used for following five purposes.
(1) Temporary data
The data which are exchanged with SDRAM using DMA. The data stored in this area are transmitting and
receiving indications and first cell of IP packet.
(2) Flow table pool
The area in which Flow tables is stored.
(3) Packet Info structure
The area in which Packet Info structures is stored.
(4) Receive free buffer pool
The are in which “pool descriptors” is stored. Each pool descriptors uses 2 words.
(5) VC table pool
The area in which transmit and receive VC Tables is stored. Each VC table uses 1 block (16 words).