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| Table 4 - Status Register |
BIT | BIT NAME | SYMBOL | DESCRIPTION |
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7 | Receiver | RI | This bit, if high, indicates that the receiver is not enabled because either |
| Inhibited |
| an "Enable Receive to Page fnn" command was never issued, or a |
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| packet has been deposited into the RAM buffer page fnn as specified by |
|
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| the last "Enable Receive to Page fnn" command. No messages will be |
|
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| received until this command is issued, and once the message has been |
|
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| received, the RI bit is set, thereby inhibiting the receiver. The RI bit is |
|
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| cleared by issuing an "Enable Receive to Page fnn" command. This bit, |
|
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| when set, will cause an interrupt if the corresponding bit of the Interrupt |
|
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| Mask Register (IMR) is also set. When this bit is set and another |
|
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| station attempts to send a packet to this station, this station will send a |
|
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| NAK. |
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|
6,5 | (Reserved) |
| These bits are undefined. |
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|
4 | Power On Reset | POR | This bit, if high, indicates that the COM20020 has been reset by either a |
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| software reset, a hardware reset, or writing 00H to the Node ID |
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| Register. The POR bit is cleared by the "Clear Flags" command. |
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3 | Test | TEST | This bit is intended for test and diagnostic purposes. It is a logic "0" |
|
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| under normal operating conditions. |
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2 | Reconfiguration | RECON | This bit, if high, indicates that the Line Idle Timer has timed out because |
|
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| the RXIN pin was idle for 82μS. The RECON bit is cleared during a |
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| "Clear Flags" command. This bit, when set, will cause an interrupt if the |
|
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| corresponding bit in the IMR is also set. The interrupt service routine |
|
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| should consist of examining the MYRECON bit of the Diagnostic Status |
|
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| Register to determine whether there are consecutive reconfigurations |
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| caused by this node. |
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|
1 | Transmitter | TMA | This bit, if high, indicates that the packet transmitted as a result of an |
| Message |
| "Enable Transmit from Page fnn" command has been acknowledged. |
| 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 |
|
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| by issuing the "Enable Transmit from Page fnn" command. |
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|
0 | Transmitter | TA | This bit, if high, indicates that the transmitter is available for |
| Available |
| 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 |
|
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| Page fnn" command after the node next receives the token. This bit, |
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| when set, will cause an interrupt if the corresponding bit in the IMR is |
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| also set. |
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25
