IDT SMBus Interfaces
PES24N3A User Manual
6 - 9
April 10, 2008
Notes
System Design Recommendations
1. I/O expander addresses and default output values may be configured during serial EEPROM initial-
ization. If I/O expander addresses are configured via the serial EEPROM, then the PES24N3A will
initialize the I/O expanders when normal device operation begins following the completion of the
fundamental reset sequence.
2. If the I/O expanders are initialized via serial EEPROM, then the data value for output signals during
the SMBus initialization sequence will correspond to those at the time the SMBus transactions are
initiated. It is not possible to toggle SMBus I/O expander outputs by modifying data values during
serial EEPROM initialization.
3. During a fundamental reset and before the I/O expander outputs are initialized, all I/O expander
output signals default to inputs. Therefore, pull-up or pull-down resistors should be placed on
outputs to ensure that they are held in the desired state during this period.
4. All hot-plug data value modifications that correspond to hot-plug outputs result in SMBus transac-
tions. This includes modifications due to upstream secondary bus resets and hot-resets.
5. I/O expander outputs are not modified when the device transitions from normal operation to a funda-
mental reset. In systems where I/O expander output values must be reset during a fundamental
reset, a PCA9539 I/O expander should be used.
I/O Expander 0
SMBus I/O
Expander
Bit
Type
Signal
Description
0 (I/O-0.0)
1
1.
I/O-x.y corresponds to the notation used for PCA9555 port x I/O pin y.
I
P2APN
Port 2 attention push button input
1 (I/O-0.1)
I
P2PDN
Port 2 presence detect input
2 (I/O-0.2)
I
P2PFN
Port 2 power fault input
3 (I/O-0.3)
I
P2MRLN
Port 2 manually-operated retention latch
(MRL) input
4 (I/O-0.4)
O
P2AIN
Port 2 attention indicator output
5 (I/O-0.5)
O
P2PIN
Port 2 power indicator output
6 (I/O-0.6)
O
P2PEP
Port 2 power enable output
7 (I/O-0.7)
O
P2ILOCKP
Port 2 electromechanical interlock
8 (I/O-1.0)
I
P4APN
Tie high
9 (I/O-1.1)
I
P4PDN
Tie high
10 (I/O-1.2)
I
P4PFN
Tie high
11 (I/O-1.3)
I
P4MRLN
Tie high
12 (I/O-1.4)
O
P4AIN
Tie high or low
13 (I/O-1.5)
O
P4PIN
Tie high or low
14 (I/O-1.6)
O
P4PEP
Tie high or low
15 (I/O-1.7)
O
P4ILOCKP
Tie high or low
Table 6.5 I/O Expander 0 Signals
Summary of Contents for 89HPES24N3A
Page 10: ...IDT Table of Contents PES24N3A User Manual iv April 10 2008 Notes...
Page 12: ...IDT List of Tables PES24N3A User Manual vi April 10 2008 Notes...
Page 14: ...IDT List of Figures PES24N3A User Manual viii April 10 2008 Notes...
Page 18: ...IDT Register List PES24N3A User Manual xii April 10 2008 Notes...
Page 64: ...IDT Link Operation PES24N3A User Manual 4 8 April 10 2008 Notes...
Page 88: ...IDT Power Management PES24N3A User Manual 7 4 April 10 2008 Notes...
Page 160: ...IDT Configuration Registers PES24N3A User Manual 9 66 April 10 2008 Notes...