VT6516 ETC, VT6516 Datasheet - Page 48

• Manufacturer Part Number: VT6516
• Description: 16/12 PORT 10/1000 ASE T/TX
• Manufacturer: ETC

4C-
4FH
50-
53H
4.4 Registers of Buffer Control Module
* Base Address: 1000H
Addres
s
(offset
)
00-02H
08H
03-05H Bank 1 Free Pointer
06-
Congestion Factor of Output Port 15
Congestion Factor of Output Port 16 (CPU port)
There are 11 bits are used for reading FREEMCNT. Only 15 bits are
used as CPU port’s congestion factor. The read sequence of
CONGEST_FCT16[14:0] is as follows:
1. Read 0C50H to get the lowest byte.
2. Read 0C51H to get the other 7 bits.
Function
Bank 0 Free Pointer
This register is initialized according to SDRAMTYPE while the
CFP is written. For 16/64Mbit SDRAM, its value is always 128
because the bank 0 free list follows the private buffer pool of buffer
entries 0~127. The free buffers with starting address at the SDRAM
even bank should be linked into this free list to improve the SDRAM
bandwidth utilization. However, if the free buffers are misplaced,
they will returned to the adequate free lists after their first release by
the output port control. Internally, the free pointer refers to the ID of
the 1st free buffer, rather than its physical address in SRAM (that is
equal to ID*3).
This register is initialized according to SDRAMTYPE while the
CFP is written. For 16Mbit SDRAM, its value is 130. For 64Mbit
SDRAM, its value is 131. The fixed buffer size is 1536 bytes.
Because the page size is 2KB for 16Mbit SDRAM, the first public
buffer of bank 1 is the 130th entry located at page 1. Because the
page size is 4KB for 64Mbit SDRAM, the first public buffer of bank
1 is the 131
Free Memory Block Count
It is an integer value <= sizeof(SDRAM) / 1.5KB. It has to be
specified at the switch initialization stage.
To fix the bug of reading FREEMCNT in VT3061A, the bit
mapping for reading FREEMCNT is modified in VT3061B.
The write sequence of FREEMCNT is also to write data to
1006H, 1007H, 1008H. However, the read sequence of
FREEMCNT has to read data from
(1) Read 1006H to get the lowest byte, and also lock the
(2) Read 0C52H to get the second byte, i.e.
(3) Read 0C53H to get the FREEMCNT[17:16]
(4) Read 0C51H to get the FREEMCNT[18]
CONGEST16[7:0] = HD[7:0]
CONGEST16[14:8] = HD[6:0]
counter information, .i.e. FREEMCNT[7:0] = HD[7:0]
FREEMCNT[15:8] = HD[7:0]
FREEMCNT[17:16] = HD[1:0]
FREEMCNT[18] = HD[7]
VIA Technologies, Inc.
st
entry located at page 1.
-48-
Preliminary VT6516 Datarsheet
CONGEST_F
CT15
CONGEST_F
CT16
Register
Name
FREE0_PT [18:0
FREE1_PT [18:0
FREEMC
NT
[25:0]
[25:0]
Bits Defau
]
]
[18:0
]
0
0
lt
Value
R/O
R/O
R/
W
R/O
R/O
R/
W