COM20022I_06 Datasheet, PDF (39/82 Pages) SMSC Corporation – 10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM

10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM
Datasheet
DATA
0000 0000
0000 0001
0000 0010
b0fn n100
00fn n011
0000 c101
000r p110
0000 1000
0001 1000
0001 0000
COMMAND
Clear
Transmit
Interrupt
Disable
Transmitter
Disable
Receiver
Enable
Receive to
Page fnn
Enable
Transmit from
Page fnn
Define
Configuration
Clear Flags
Clear
Receive
Interrupt
Start Internal
Operation
Clear Mask bit of
DMAEND
Table 6.5 - Command Register
DESCRIPTION
This command is used only in the Command Chaining operation. Please
refer to the Command Chaining section for definition of this command.
This command will cancel any pending transmit command (transmission
that has not yet started) and will set the TA (Transmitter Available) status
bit to logic "1" when the COM20022I next receives the token.
This command will cancel any pending receive command. If the
COM20022I is not yet receiving a packet, the RI (Receiver Inhibited) bit
will be set to logic "1" the next time the token is received. If packet
reception is already underway, reception will run to its normal
conclusion.
This command allows the COM20022I to receive data packets into RAM
buffer page fnn and resets the RI status bit to logic "0". The values
placed in the "nn" bits indicate the page that the data will be received
into (page 0, 1, 2, or 3). If the value of "f" is a logic "1", an offset of 256
bytes will be added to that page specified in "nn", allowing a finer
resolution of the buffer. Refer to the Selecting RAM Page Size section
for further detail. If the value of "b" is logic "1", the device will also
receive broadcasts (transmissions to ID zero). The RI status bit is set to
logic "1" upon successful reception of a message.
This command prepares the COM20022I to begin a transmit sequence
from RAM buffer page fnn the next time it receives the token. The
values of the "nn" bits indicate which page to transmit from (0, 1, 2, or 3).
If "f" is logic "1", an offset of 256 bytes is the start of the page specified in
"nn", allowing a finer resolution of the buffer. Refer to the Selecting RAM
Page Size section for further detail. When this command is loaded, the
TA and TMA bits are reset to logic "0". The TA bit is set to logic "1" upon
completion of the transmit sequence. The TMA bit will have been set by
this time if the device has received an ACK from the destination node.
The ACK is strictly hardware level, sent by the receiving node before its
microcontroller is even aware of message reception. Refer to Figure 3.1
for details of the transmit sequence and its relation to the TA and TMA
status bits.
This command defines the maximum length of packets that may be
handled by the device. If "c" is a logic "1", the device handles both long
and short packets. If "c" is a logic "0", the device handles only short
packets.
This command resets certain status bits of the COM20022I. A logic "1"
on "p" resets the POR status bit and the EXCNAK Diagnostic status bit.
A logic "1" on "r" resets the RECON status bit.
This command is used only in the Command Chaining operation. Please
refer to the Command Chaining section for definition of this command.
This command restarts the stopped internal operation after changing
CKUP1 or CKUP0 bit.
This command resets a mask bit of the DMAEND. It is for clearing
interrupt by DMA transfer finished.
SMSC COM20022I
Page 39
DATASHEET
Revision 02-27-06