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Table 4 - Status Register
BIT BIT NAME SYMBOL DESCRIPTION
7 Receiver
Inhibited
RI This bit, if high, indicates that the receiver is not enabled because either
an "Enable Receive to Page fnn" command was never issued, or a
packet has been deposited into the RAM buffer page fnn as specified by
the last "Enable Receive to Page fnn" command. No messages will be
received until this command is issued, and once the message has been
received, the RI bit is set, thereby inhibiting the receiver. The RI bit is
cleared by issuing an "Enable Receive to Page fnn" command. This bit,
when set, will cause an interrupt if the corresponding bit of the Interrupt
Mask Register (IMR) is also set. When this bit is set and another
station attempts to send a packet to this station, this station will send a
NAK.
6,5 (Reserved) These bits are undefined.
4 Power On Reset POR This bit, if high, indicates that the COM20020 has been reset by either a
software reset, a hardware reset, or writing 00H to the Node ID
Register. The POR bit is cleared by the "Clear Flags" command.
3 Test TEST This bit is intended for test and diagnostic purposes. It is a logic "0"
under normal operating conditions.
2 Reconfiguration RECON This bit, if high, indicates that the Line Idle Timer has timed out because
the RXIN pin was idle for 82µS. The RECON bit is cleared during a
"Clear Flags" command. This bit, when set, will cause an interrupt if the
corresponding bit in the IMR is also set. The interrupt service routine
should consist of examining the MYRECON bit of the Diagnostic Status
Register to determine whether there are consecutive reconfigurations
caused by this node.
1 Transmitter
Message
Acknowledged
TMA This bit, if high, indicates that the packet transmitted as a result of an
"Enable Transmit from Page fnn" command has been acknowledged.
This bit should only be considered valid after the TA bit (bit 0) is set.
Broadcast messages are never acknowledged. The TMA bit is cleared
by issuing the "Enable Transmit from Page fnn" command.
0 Transmitter
Available
TA This bit, if high, indicates that the transmitter is available for
transmitting. This bit is set when the last byte of scheduled packet has
been transmitted out, or upon execution of a "Disable Transmitter"
command. The TA bit is cleared by issuing the "Enable Transmit from
Page fnn" command after the node next receives the token. This bit,
when set, will cause an interrupt if the corresponding bit in the IMR is
also set.