When RST is active, REQ is an input for NAND tree
testing.
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.
RST
Reset
Input
When RST is asserted LOW and the PG pin is HIGH,
then the Am79C978 controller performs an internal
system reset of the type H_RESET
(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 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
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.
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.
SERR
System Error
Output
The PME signal is asynchronous with respect to the
PCI clock. See the Power Saving Mode section for de-
tailed description.
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.
PG
Power Good
Input
By default SERR is an open-drain output. For compo-
nent test, it can be programmed to be an active-high
totem-pole output.
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 RST is active, SERR is an input for NAND tree
testing.
When PG is LOW and either MPPEN or MPMODE is
set to 1, the device enters Magic Packet mode.
STOP
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.
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 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
When RST is active, STOP is an input for NAND tree
testing.
testing.
Board Interface
TRDY
Note: Before programming the LED pins, see the
description of LEDPE in BCR2, bit 12.
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.
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-
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.
28
Am79C978
AMD [ AMD ]
