DM9008 Ver la hoja de datos (PDF) - Davicom Semiconductor, Inc.
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DM9008 Datasheet PDF : 68 Pages
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Command Register (CR)
The Command Register is used to initiate transmissions,
enable or disable Remote DMA operations, and select register
pages. To issue a command, the microprocessor sets the
corresponding bit(s) (RD2, RD1, RD0, TXP). Further
commands may be overlapped, but with the following rules: (1)
If a transmit command overlaps a remote DMA operation, bits
RD0, RD1, and RD2 must be maintained for the remote DMA
command when the TXP bit is set. Note that if a remote DMA
command is re-issued when the transmit command is given,
7
6
5
4
PS1
PS0
RD2
RD1
DM9008
ISA/Plug & Play Super Ethernet Contoller
the DMA will be completed immediately if the remote byte
count register has not been reinitialized. (2) If a remote DMA
operation overlaps a transmission, RD0, RD1, and RD2 may
be written with the desired values and a "0" may be written to
the TXP bit. Writing a "0" to this bit has no effect. (3) A remote
write DMA may not overlap a remote read operation or vice
versa. Either of these operations must either be completed or
be aborted before the other operation may start. Bits PS1,
PS0, RD2 and STP may be set at any time.
3
2
1
0
RD0
TXP
STA
STP
Bit
Symbol
Description
D0
STP
STOP: Software reset command. Takes the controller off-line, and no packets will be received
or transmitted. Any reception or transmission in progress will continue to completion before the
reset state is entered. To exit this state, the STP bit must be reset. The software reset is
executed only when indicated by the RST bit in the ISR being set to a "1." STP powers up
high
D1
STA
Start mode
D2
TXP
Transmit Packet: This bit must be set to initiate transmission of a packet. TXP is internally reset
after the transmission is either completed or aborted. This bit should be set only after the
Transmit Byte Count and Transmit Page Start registers have been programmed. TXP powers
up low
D3
RD0
Remote DMA Command: These three encoded bits control operation of the Remote DMA
D4
RD1
channel. RD2 can be set to abort any Remote DMA command in progress. The Remote
D5
RD2
Byte Count Registers should be cleared when a Remote DMA has been aborted. The
Remote Start Addresses are not restored to the starting address if the Remote DMA is
aborted. RD2 powers up high
RD2 RD1 RD0
0
0
0
Not Allowed
0
0
1
Remote Read
0
1
0
Remote Write
0
1
1
Send Packet
1
X
X
Abort/Complete Remote DMA
D6
PS0
Page Select: These two encoded bits select which register page is to be accessed with
D7
PS1
addresses SA0-3
PS1 PS0
0
0
Register Page 0
0
1
Register Page 1
1
0
Register Page 2
1
1
Register Page 3
Final
15
Version: DM9008-DS-F02
November 30, 2000
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