System Interface Pins
Table 49 gives the state of the interface pins in the powerdown state. Pins unaffected by the powerdown are labeled
"Unchanged".
Table 49 – State of System Pins in Auto Powerdown
SYSTEM PINS
LAD[3:0]
STATE IN AUTO POWERDOWN
Unchanged
nLDRQ
Unchanged
nLPCPD
Unchanged
nLFRAME
nPCI_RESET
PCI_CLK
Unchanged
Unchanged
Unchanged
SER_IRQ
Unchanged
FDD Interface Pins
All pins in the FDD interface which can be connected directly to the floppy disk drive itself are either DISABLED or
TRISTATED.
Pins used for local logic control or part programming are unaffected. Table 50 depicts the state of the floppy disk drive
interface pins in the powerdown state.
Table 50 - State of Floppy Disk Drive Interface Pins in Powerdown
FDD PINS
STATE IN AUTO POWERDOWN
INPUT PINS
Input
nRDATA
nWRTPRT
nTRK0
Input
Input
nINDEX
Input
nDSKCHG
Input
OUTPUT PINS
Tristated
Tristated
Active
nMTR0
nDS0
nDIR
nSTEP
Active
nWDATA
nWGATE
nHDSEL
DRVDEN[0:1]
Tristated
Tristated
Active
Active
UART Power Management
Direct power management is controlled by CR22. Refer to CR22 for more information.
Auto Power Management is enabled by CR23-B4 and B5. When set, these bits allow the following auto power
management operations:
1. The transmitter enters auto powerdown when the transmit buffer and shift register are empty.
2. The receiver enters powerdown when the following conditions are all met:
A. Receive FIFO is empty
B. The receiver is waiting for a start bit.
Note:
While in powerdown the Ring Indicator interrupt is still valid and transitions when the RI input changes.
Exit Auto Powerdown
The transmitter exits powerdown on a write to the XMIT buffer. The receiver exits auto powerdown when RXDx
changes state.
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