Chapter 12: 10/100 IEEE802.3 Media Access Controller
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
12-9
Bit(s)
Field
R/W
Description
7:5
PBL
R/W
Programmable Burst Length (011)
Indicates the maximum number of 8-byte values to be transferred in one DMA
transaction.
X00 2 (16 bytes)
X01 4 (32 bytes)
X10 8 (64 bytes)
X11 16 (128 bytes)
It is also a kind of count threshold, and has different definitions in the TxFIFO and the
RxFIFO. This threshold guarantees that a PBL space of at least 8 bytes is either free
to write to the TxFIFO or to contain data to read from the Rx_FIFO.
4
BAR
R/W
Bus Arbitration
Selects the internal bus arbitration between the receive and transmit processes. When
set, a round-robin arbitration scheme is applied resulting in equal sharing between
processes. When reset, the receive process has priority over the transmit process. (0)
3
CntRst
R/W
Counter Reset. This bit provides counter reset only. It will be kept active for at least 40
gbsBusClk periods. This bit is self-clearing. (0)
2
RxRst
R/W
Receive Port Reset. This bit provides Receive Port reset only. This bit is self-clearing.
(0)
1
TxRst
RW
Transmit Port Reset. This bit provides Transmit Port reset only. This bit is self-
clearing. (0)
0
SwRst
RW
Software Reset. Reset is immediate and it is equivalent to resetting the counters, the
transmitters, the receivers, and the MII management block. It does not affect registers,
including interrupt status or diagnostic registers. This bit is self-clearing. (0)
Note: The Busy bit in the MII control register must be 0 before this bit is set.
12.3.1.2 Transmit Frame Configuration Register (TFCReg)
The Transmit Frame Configuration Register defines the transmission rules for the MAC.
These can be changed to accommodate different options. Upon the completion of reset, this
register’s default value is 0x2008_0100.
31
30
28
27
26
25
24
23
16
0
TxFIFOSize
TxFlw
Cnt
TxSQE
En
0
TxSOFTh[7:0]
1
3
1
1
2
8
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Hw
Dup
Self
En
F
Dup
Loop
En
Loop
Sel
TxEn
CRC
Sel
TxEn
CRC
TxEn
Pad
TxEn
Halt
TxRetry
Sel
Tx
BOff
Sel
TxAb
Defer
TxPreAm
Sel
Tx
Start
Tx
Ena-
ble
1
1
1
1
1
1
1
1
2
1
1
2
1
1
Table 12-8 TFCReg Register Field Descriptions
Bit(s)
Field
R/W
Description
31
–
R/O
Reserved
30:28
TxFifoSize
[2:0]
R/W
TxFIFO Size Select (010)
010
: Size = 1 KB (128 x 64 bits)
000, 001, 011-111 : Reserved. Try to avoid changing these values.
27
TxFlwCnt
R/W
Transmit Flow Control
This bit must remain cleared. Do not try to set this bit.
26
TxSQEEn
R/W
SQE Test Enable (0)
When TxSQE is 0, the transmitter does not report the status of the SQE test performed by
Содержание TMPR7901
Страница 1: ...TX System RISC TX79 Family TMPR7901 Symmetric 2 way superscalar 64 bit CPU ...
Страница 14: ...Handling Precautions ...
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Страница 17: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Страница 41: ...4 Precautions and Usage Considerations 4 2 ...
Страница 42: ...TX7901 User s Manual Rev 6 30T November 2001 DOCUMENT NUMBER M 99 00004 07 ...
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