dp83261 National Semiconductor Corporation, dp83261 Datasheet - Page 56

• Manufacturer Part Number: dp83261
• Description: Bmac Device Fddi Media Access Controller
• Manufacturer: National Semiconductor Corporation

6 0 Control Information
6 5 3 Claim Information Requested Target Token Rotation Time (TREQ)
The Requested Target Token Rotation Time (TREQ) is stored in registers TREQ0 – TREQ3 TREQ(31 – 0) is represented as a
negative two’s complement number This value is transmitted in all Claim frames generated by the Ring Engine
Bits TREQ(31 – 24) are always transmitted as and compared with FFh and bits TREQ(7 – 0) are always transmitted as and
compared with 00h independent of the value stored in the MAC Parameter RAM TREQ is therefore programmable with
20 48 ms resolution and a maximum value of 1 34 seconds
ACCESS RULES
6 5 4 Beacon Information Transmit Beacon Type (TBT)
Transmit Beacon Type 0 – 3 (TBT0 – 3) represents the Transmit Beacon Type to be transmitted in the information field of a
Beacon frame
When the Beacon state is reached as a result of a failed Claim process the first byte of the Beacon Information field bits
TBT31 – 24 are forced to Zero to produce a Beacon Type 0 as required by the MAC Standard Bits TBT(23 – 0) are transmitted
as the rest of the Information field
When the Beacon state is reached as a result of a Beacon Request (when Function BCN is set) bits TBT(31 – 0) are transmitted
as the Information field Bit TBT(0) is transmitted last
ACCESS RULES
TREQ0
TREQ1
TREQ2
TREQ3
TBT0
TBT1
TBT2
TBT3
Address
Address
50 – 53h
54 – 57h
TREQ(31)
TREQ(23)
TREQ(15)
TREQ(7)
TBT(31)
TBT(23)
TBT(15)
TBT(7)
D7
D7
Stop Mode
Stop Mode
Read
Read
TREQ(30)
TREQ(22)
TREQ(14)
TREQ(6)
TBT(30)
TBT(22)
TBT(14)
TBT(6)
D6
D6
(Continued)
Stop Mode
Stop Mode
TREQ(29)
TREQ(21)
TREQ(13)
TREQ(5)
TBT(29)
TBT(21)
TBT(13)
TBT(5)
Write
Write
D5
D5
TREQ(28)
TREQ(20)
TREQ(12)
TREQ(4)
TBT(28)
TBT(20)
TBT(12)
TBT(4)
D4
D4
56
TREQ(27)
TREQ(19)
TREQ(11)
TREQ(3)
TBT(27)
TBT(19)
TBT(11)
TBT(3)
D3
D3
TREQ(26)
TREQ(18)
TREQ(10)
TREQ(2)
TBT(26)
TBT(18)
TBT(10)
TBT(2)
D2
D2
TREQ(25)
TREQ(17)
TREQ(9)
TREQ(1)
TBT(25)
TBT(17)
TBT(9)
TBT(1)
D1
D1
TREQ(24)
TREQ(16)
TREQ(8)
TREQ(0)
TBT(24)
TBT(16)
TBT(8)
TBT(0)
D0
D0