DP83256 Datasheet, PDF (43/144 Pages) National Semiconductor (TI) – PLAYERa+™ Device (FDDI Physical Layer Controller)

5 0 Registers (Continued)
5 1 MODE REGISTER (MR)
The Mode Register is used to initialize and configure the PLAYERa device
ACCESS RULES
ADDRESS
00h
READ
Always
WRITE
Always
D7
D6
D5
RNRZ
TNRZ
TE
D4
TQL
D3
D2
CM
LILB
D1
SILB
D0
RUN
Bit Symbol
Description
D0 RUN
RUN ESTOP
0 Enables the STOP mode Refer to section 4 2 STOP MODE for more information
1 Normal operation (i e RUN mode)
Note The RUN bit is automatically set to 0 when the ERST pin is asserted (i e set to ground)
D1 SILB
SHORT INTERNAL LOOPBACK
0 Disables Internal Loopback mode (i e normal operation)
1 Enables Internal Loopback mode
Refer to section 4 3 LOOPBACK MODE for more information
D2 LILB
LONG INTERNAL LOOPBACK
0 Disables Long Internal Loopback mode (i e normal operation)
1 Enables Long Internal Loopback mode
Note Long Internal Loopback should not be used when the Alternate PMD Interface is enabled
Refer to section 4 3 LOOPBACK MODE for more information
D3 CM
CASCADE MODE
0 Disables synchronization of cascaded PLAYERa devices
1 Enables the synchronization of cascaded PLAYERa devices
Refer to section 4 4 CASCADE MODE for more information
Note Cascade Mode is only available on the DP83257 device The other devices do not have the required CS and CR pins Do not set this bit for
any device but the DP83257
D4 TQL
TRANSMIT QUIET LEVEL This bit is used to program the transmission level of the Quiet symbols during Off
Transmit mode (OTM) only
0 Low (PMD OFF) level Quiet symbols are transmitted through the PMD Data Request pins (i e PMRD a e low
PMRD b e high)
1 High (PMD ON) level Quiet symbols are transmitted through the PMD Data Request pins (i e PMRD a e high
PMRD b e low)
D5 TE
TRANSMIT ENABLE The TE bit controls the action of the PMD transmitter Enable (TXE) pin When TE is 0 the
TXE output disables the PMD transmitter when TE is 1 the PMD transmitter is disabled during the Off Transmit
Mode (OTM) and enabled otherwise The On and Off level of the TXE is depended on the PMD transmitter Enable
Level (TEL) pin to the PLAYERa device The following rules summaries the output of TXE
1 If TEe0 then TXEeOff
2 If TEe1 and OTM then TXEeOff
3 If TEe1 and not OTM then TXEeOn
D6 TNRZ TRANSMIT NRZ DATA
0 Transmits data in Non-Return-To-Zero-Invert-On-Ones (NRZI) format (normal format)
1 Transmits data in Non-Return-To-Zero format (NRZ)
D7 RNRZ RECEIVE NRZ DATA
0 Receives data in Non-Return-To-Zero-Invert-On-Ones format (NRZI) (normal format)
1 Receives data in Non-Return-To-Zero format (NRZ)
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