IDT SMBus Interfaces
PES12T3G2 User Manual
5 - 9
January 28, 2013
Notes
For example, a user who neglects to configure a GPIO as an alternate function may use this feature to
determine that master SMBus transactions to the I/O expander function properly and that the issue is with
the interrupt logic.
The IO Expander Test Mode (IOEXTM) bit in the IOEXPTINF register allows an I/O expander test mode
to be entered. When this bit is set, Whitney core logic outputs are ignored and the values written to the I/O
expander for output bits are the values in the IOEDATA field. In this mode, the PES12T3G2 issues a trans-
action to update the state of the I/O expander whenever a bit corresponding to an I/O expander output
changes state due to a write to the IOEDATA field. Bits in the IOEDATA field that correspond to outputs are
dependent on the I/O expander number selected in the SEL field in the IOEXPINTF register. The outputs for
each I/O expander number are shown in Tables 5.6 through 5.8.
System design recommendations include:
–
I/O expander addresses and default output values may be configured during serial EEPROM
initialization. If I/O expander addresses are configured via the serial EEPROM, then the
PES12T3G2 will initialize the I/O expanders when normal device operation begins following the
completion of the Fundamental Reset sequence.
–
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 transac-
tions are initiated. It is not possible to toggle SMBus I/O expander outputs by modifying data
values during serial EEPROM initialization.
–
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.
–
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.
–
I/O expander outputs are not modified when the device transitions from normal operation to a
Fundamental Reset. In systems where I/O expander output values must be reset during a Funda-
mental 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
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
Port 4 attention push button input
9 (I/O-1.1)
I
P4PDN
Port 4 presence detect input
10 (I/O-1.2)
I
P4PFN
Port 4 power fault input
11 (I/O-1.3)
I
P4MRLN
Port 4 manually-operated retention latch (MRL) input
12 (I/O-1.4)
O
P4AIN
Port 4 attention indicator output
Table 5.6 I/O Expander 0 Signals (Part 1 of 2)
Summary of Contents for 89HPES12T3G2
Page 10: ...IDT Table of Contents PES12T3G2 User Manual iv January 28 2013 Notes...
Page 12: ...IDT List of Tables PES12T3G2 User Manual vi January 28 2013 Notes...
Page 14: ...IDT List of Figures PES12T3G2 User Manual viii January 28 2013 Notes...
Page 18: ...IDT Register List PES12T3G2 User Manual xii January 28 2013 Notes...
Page 46: ...IDT Link Operation PES12T3G2 User Manual 3 10 January 28 2013 Notes...
Page 66: ...IDT SMBus Interfaces PES12T3G2 User Manual 5 18 January 28 2013 Notes...
Page 70: ...IDT Power Management PES12T3G2 User Manual 6 4 January 28 2013 Notes...
Page 138: ...IDT Configuration Registers PES12T3G2 User Manual 8 62 January 28 2013 Notes...
