COM90C66 Datasheet, PDF (25/76 Pages) SMSC Corporation – ARCNET Controller/Transceiver with AT Interface and On-Chip RAM

Table 7 - Command Register
WRITTEN DATA COMMAND NAME
DESCRIPTION
000n n011
ENABLE TRANSMIT
FROM PAGE nn
This command prepares the COM90C66 to begin a
transmit sequence from RAM buffer page nn the next
time it receives the token. 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 COM90C66 has received an acknowledgement from
the destination node. This acknowledgement is strictly
hardware level, which is sent by the receiving node before
its controlling processor is even aware of message
reception. It is also possible for this acknowledgement to
get lost due to line errors. This implies that the TMA bit is
not a guarantee of proper destination reception. Refer to
Figure 1 for details of the transmit sequence and its
relation to the TA and TMA status bits.
b00n n100
ENABLE RECEIVE
TO PAGE nn
This command allows the COM90C66 to receive data
packets into RAM buffer page nn and resets the RI status
bit to logic "0". If the value of "b" is a logic "1", the
COM90C66 will also receive broadcast transmission. A
broadcast transmission is a transmission to ID zero. The
RI status bit is set to logic "1" upon successful reception
of a message.
0000 c101
DEFINE
CONFIGURATION
This command defines the maximum length of packets
that may be handled by the device. If the value of "c" is a
logic "1", the COM90C66 will handle long as well as short
packets. If the value of "c" is a logic "0", the COM90C66
will only handle short packets (packets less than 254
bytes).
000r p110 CLEAR FLAGS
This command resets one or both flags of the
COM90C66. If the value of "p" is a logic "1", the POR
status flag is reset. If the value of "r" is a logic "1", the
RECON status flag is reset.
0000 1000
CLEAR RECEIVE
INTERRUPT
This command is only used in the Command Chaining
operation. Please refer to the Command Chaining
section of this document for definition of this command.
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