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COM20019I-HT Datasheet(PDF) 32 Page - SMSC Corporation |
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COM20019I-HT Datasheet(HTML) 32 Page - SMSC Corporation |
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32 / 65 page  Low Cost ARCNET (ANSI 878.1) Controller with 2K x 8 On-Board RAM Rev. 03-07-06 Page 32 SMSC COM20019I DATASHEET BIT BIT NAME SYMBOL DESCRIPTION 4,3 Extended Timeout 1,2 ET1, ET2 These bits allow the network to operate over longer distances than the default maximum 32 miles by controlling the Response, Idle, and Reconfiguration Times. All nodes should be configured with the same timeout values for proper network operation. For the COM20019I with a 20 MHz crystal oscillator, the bit combinations follow: ET2 0 0 1 1 ET1 0 1 0 1 Response Time (mS) 9.548 4.774 2.387 0.597 Idle Time (mS) 10.496 5.248 2.624 0.656 Reconfig Time (S) 13.44 13.44 13.44 6.72 Note: These values are for 312.5 Kbps and RCNTMR[1,0]=00. Reconfiguration time is changed by the RCNTMR1 and RCNTMR0 bits. 2 Backplane BACK- PLANE A logic "1" on this bit puts the device into Backplane Mode signaling which is used for Open Drain and Differential Driver interfaces. This bit must be set to ‘1’ at the COM20019I. 1,0 Sub Address 1,0 SUBAD 1,0 These bits determine which register at address 07 may be accessed. The combinations are as follows: SUBAD1 SUBAD0 Register 0 0 Tentative I 0 1 Node ID 1 0 Setup 1 1 1 Next ID See also the Sub Address Register. Table 6.10 - Setup 1 Register BIT BIT NAME SYMBOL DESCRIPTION 7 Pulse1 Mode P1MODE This bit determines the type of PULSE1 output driver used in Backplane Mode. When high, a push/pull output is used. When low, an open drain output is used. The default is open drain. 6 Four NACKS FOUR NACKS This bit, when set, will cause the EXNACK bit in the Diagnostic Status Register to set after four NACKs to Free Buffer Enquiry are detected by the COM20019I. This bit, when reset, will set the EXNACK bit after 128 NACKs to Free Buffer Enquiry. The default is 128. 5 Reserved Do not set. 4 Receive All RCVALL This bit, when set, allows the COM20019I to receive all valid data packets on the network, regardless of their destination ID. This mode can be used to implement a network monitor with the transmitter on- or off-line. Note that ACKs are only sent for packets received with a destination ID equal to the COM20019I's programmed node ID. This feature can be used to put the COM20019I in a 'listen-only' mode, where the transmitter is disabled and the COM20019I is not passing tokens. Defaults low. |
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