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AM79C978VC/W 数据表(PDF) 28 Page - Advanced Micro Devices |
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AM79C978VC/W 数据表(HTML) 28 Page - Advanced Micro Devices |
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28 / 261 page ![]() 28 Am79C978 When RST is active, REQ is an input for NAND tree testing. RST Reset Input When RST is asserted LOW and the PG pin is HIGH, then the Am79C978 controller performs an internal syste m r e set of the t y pe H _ R ESET (HARDWARE_RESET, see section on RESET). RST must be held for a minimum of 30 clock periods. While in the H_RESET state, the Am79C978 controller will disable or deassert all outputs. RST may be asynchro- nous to clock when asserted or deasserted. When the PG pin is LOW, RST disables all of the PCI pins except the PME pin. When RST is LOW and PG is HIGH, NAND tree testing is enabled. SERR System Error Output During any slave transaction, the Am79C978 controller asserts SERR when it detects an address parity error, and reporting of the error is enabled by setting PER- REN (PCI Command register, bit 6) and SERREN (PCI Command register, bit 8) to 1. By default SERR is an open-drain output. For compo- nent test, it can be programmed to be an active-high totem-pole output. When RST is active, SERR is an input for NAND tree testing. STOP Stop Input/Output In slave mode, the Am79C978 controller drives the STOP signal to inform the bus master to stop the cur- rent transaction. In bus master mode, the Am79C978 controller checks STOP to determine if the target wants to disconnect the current transaction. When RST is active, STOP is an input for NAND tree testing. TRDY Target Ready Input/Output TRDY indicates the ability of the target of the transac- tion to complete the current data phase. Wait states are inserted until both IRDY and TRDY are asserted simul- taneously. A data phase is completed on any clock when both IRDY and TRDY are asserted. When the Am79C978 controller is a bus master, it checks TRDY during all read data phases to determine if valid data is present on AD[31:0]. During all write data phases, the device checks TRDY to determine if the target is ready to accept the data. When the Am79C978 controller is the target of a trans- action, it asserts TRDY during all read data phases to indicate that valid data is present on AD[31:0]. During all write data phases, the device asserts TRDY to indi- cate that it is ready to accept the data. When RST is active, TRDY is an input for NAND tree testing. Magic Packet Interface PME Power Management Event Output, Open Drain PME is an output that can be used to indicate that a power management event (a Magic Packet, an OnNow pattern match, or a change in link state) has been de- tected. The PME pin is asserted when either 1. PME_STATUS and PME_EN are both 1, 2. PME_EN_OVR and MPMAT are both 1, or 3. PME_EN_OVR and LCDET are both 1. The PME signal is asynchronous with respect to the PCI clock. See the Power Saving Mode section for de- tailed description. PG Power Good Input The PG pin has two functions: (1) it puts the device into Magic Packet mode, and (2) it blocks any resets when the PCI bus power is off. When PG is LOW and either MPPEN or MPMODE is set to 1, the device enters Magic Packet mode. When PG is LOW, a LOW assertion of the PCI RST pin will only cause the PCI interface pins (except for PME) to be put in the high impedance state. The internal logic will ignore the assertion of RST. When PG is HIGH, assertion of the PCI RST pin causes the controller logic to be reset and the configu- ration information to be loaded from the EEPROM. Note: PG input should be kept high during NAND tree testing. Board Interface Note: Before programming the LED pins, see the description of LEDPE in BCR2, bit 12. LED0 LED0 Output This output is designed to directly drive an LED. By de- fault, LED0 indicates an active link connection. This pin can also be programmed to indicate other network sta- tus (see BCR4). The LED0 pin polarity is programma- ble, but by default it is active LOW. When the LED0 pin polarity is programmed to active LOW, the output is an open drain driver. When the LED0 pin polarity is pro- |
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