dp83251 National Semiconductor Corporation, dp83251 Datasheet - Page 22

• Manufacturer Part Number: dp83251
• Description: Player Device Fddi Physical Layer Controller
• Manufacturer: National Semiconductor Corporation

5 0 Registers
MODE REGISTER (MR)
The Mode Register is used to initialize and configure the PLAYER device
In order to minimize interruptions on the network it is recommended that the PLAYER device first be put in STOP mode (i e set
the RUN bit to zero) before programming the Mode Register the Configuration Register or the Current Transmit State Register
ACCESS RULES
D0
D1
D2
D3
D4
D5
D6
D7
Bit
D7
RNRZ
ADDRESS
00h
RUN
ILB
EXLB
CM
TQL
TE
TNRZ
RNRZ
Symbol
D6
TNRZ
(Continued)
Always
READ
RUN STOP
Note The RUN bit is automatically set to 0 when the RST pin is asserted (i e set to ground)
INTERNAL LOOPBACK
Refer to Section 4 3 Loopback Mode of Operation for more information
EXTERNAL LOOPBACK
Refer to Section 4 3 Loopback Mode of Operation for more information
CASCADE MODE
Refer to Section 4 4 Cascade Mode of Operation for more information
TRANSMIT QUIET LEVEL This bit is used to program the transmission level of the Quiet
symbols
TRANSMIT ENABLE The TE bit controls the action of FOTX Enable (TXE) pin independent
of the current transmit mode When TE is 0 the TXE output disables the optical transmitter
when TE is 1 the optical transmitter is disabled during the Off Transmit Mode (OTM) and
enabled otherwise The On and Off level of the TXE is dependent on the FOTX Enable Level
(TEL) pin to the PLAYER device The following rules summarizes the output of TXE
TRANSMIT NRZ DATA
RECEIVE NRZ DATA
D5
TE
0 Enables the STOP mode Refer to Section 4 2 STOP Mode of Operation for more
1 Normal Operation (i e RUN mode)
0 Disables Internal Loopback mode (i e normal operation)
1 Enables Internal Loopback mode
0 Disables External Loopback mode (i e normal operation)
1 Enables External Loopback mode
0 Disables synchronization of cascaded PLAYER devices
1 Enables the synchronization of cascaded PLAYER devices
0 Low level Quiet symbols are transmitted through the PMD Data Request pins
1 High level Quiet symbols are transmitted through the PMD Data Request pins
(1) If TE
(2) If TE
(3) If TE
0 Transmits data in Non-Return-To-Zero-Invert-On-Ones format
1 Transmits data in Non-Return-To-Zero format
0 Receives data in Non-Return-To-Zero-Invert-On-Ones format
1 Receives data in Non-Return-To-Zero format
information
(i e TXD
(i e TXD
D4
TQL
WRITE
Always
e
e
e
a e
a e
0 then TXE
1 and OTM then TXE
1 and not OTM then TXE
low TXD
high TXD
D3
CM
e
22
b e
b e
Off
high)
low)
D2
EXLB
e
Description
0ff
e
On
D1
ILB
D0
RUN