Chapter 12: 10/100 IEEE802.3 Media Access Controller
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
12-26
12.3.1.19 Back to Back IPG Register (IPGReg)
This Register contains the first bus error address.
63
32
0
32
31
7
6
0
0
IPGT
25
7
Table 12-27 IPGReg Register Field Descriptions
Bits
Field
R/W
Description
63:7
–
R/W
Reserved (0x000)
6:0
IPGT
R/W
Back-To-Back IPG length. Default is 0x15.
Inter-Packet Gap (IPG) is the measurement between the last nibble of CRC and the first
nibble of the preamble of the next packet.
In 100 Mb Ethernet, the IPG is defined as 0.96 microseconds. In 10 Mb Ethernet, the IPG is
defined as 9.6 microseconds.
The IPG Time (IPGT) is used to space back-to-back transmit packets. The transmit state
machine has an intrinsic delay of 6 clock cycles (macxTxClk) between packets. In other
words, with IPGT set to 0, the resultant IPG will be 6 clock cycles. Thus the equation is:
IPG = ( 6 + IPGT )
×
T
where T is the period of macxTxClk.
Here is a simple chart of IPGT values for 100 Mb and 10 Mb Ethernet:
Table 12-28 Inter Packet Gap T values for 100 Mb / 10 Mb
IPGT
100 Mb
10 Mb
0x01
0.28
µ
s
2.8
µ
s
0x05
0.44
µ
s
4.4
µ
s
0x09
0.60
µ
s
6.0
µ
s
0x0D
0.76
µ
s
7.6
µ
s
0x12*
0.96
µ
s
9.6
µ
s
0x1D
1.40
µ
s
14.0
µ
s
Where T = 40
µ
s for 100 Mb and T = 400
µ
s for 10 Mb.
*:IEEE 802.3 standard recommended (0.96
µ
s/9.6
µ
s)== default
Summary of Contents for TMPR7901
Page 1: ...TX System RISC TX79 Family TMPR7901 Symmetric 2 way superscalar 64 bit CPU ...
Page 14: ...Handling Precautions ...
Page 15: ......
Page 17: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 41: ...4 Precautions and Usage Considerations 4 2 ...
Page 42: ...TX7901 User s Manual Rev 6 30T November 2001 DOCUMENT NUMBER M 99 00004 07 ...
Page 43: ......
Page 259: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 1 13 Removed ...
Page 260: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 2 ...