LPC47N237-MD SMSC [SMSC Corporation], LPC47N237-MD Datasheet - Page 82

• Manufacturer Part Number: LPC47N237-MD
• Description: 3.3V I/O CONTROLLER FOR PORT REPLICATORS AND DOCKING STATIONS
• Manufacturer: SMSC [SMSC Corporation]

15.1.10 SMBus Alert Response
15.2
Revision 0.3 (10-26-04)
The LPC47N237 does not implement the nSMBALERT response.
SMBus Isolation Logic
The SMBus Isolation Circuitry is used to control the connection of up to two devices to the SMBus. The
two pairs of SMBus pins (SCLK_1/SDAT_1, SCLK_2/SDAT_2) are individually software selectable to
connect internally to SMBus.
individually connected (one or the other) or both connected to SMBus.
Note that the SMBus slave device (GPIO Controller) in the part is always connected to the SMBus via the
SCLK/SDAT pins.
When one of the pairs of SCLK_1/SDAT_1 or SCLK_2/SDAT_2 pins are selected, the SMBus signals
from/to the SCLK/SDAT pins and the internal SMBus Slave device are passed through to/from the
selected SMBus pair. When both pairs are selected, then these devices can also communicate with each
other.
The SMBus Isolation Logic is implemented as a switch that internally connects neither, one or the other or
both devices to the SMBus as selected through the bits defined below.
The following bits are used to select the SMBus device to be isolated from the SMBus. The SMBus
Isolation register at 0x0E holds these bits.
Bits[1:0]: These bits control which pair of SMBus pins (SCLK_1/SDAT_1, SCLK_2/SDAT_2) are connected
to the SMBus.
00 = Both SMBus devices isolated from SMBus (default). In this case, both device 1 and device 2 are
isolated from the internal SMBus slave device and all external SMBus devices (including each other).
01 = SCLK_1/SDAT_1 connected to SCLK/SDAT. In this case, device 1 can communicate with the
internal SMBus slave device and any external slave devices on SMBus (excluding device 2).
10 = SCLK_2/SDAT_2 connected to SCLK/SDAT. In this case, device 2 can communicate with the internal
SMBus slave device and any external slave devices on SMBus (excluding device 1).
11 = Both SMBus devices connected to SMBus. In this case, device 1 and device 2 can communicate with
the internal SMBus slave device and any external slave devices on SMBus (including each other).
Bits[7:2] are reserved.
The following figure shows a representation of the switch in the system.
The selection allows for the two SMBus devices to be disconnected,
DATASHEET
Page 82
3.3v I/O Controller for Port Replicators and Docking Stations
SMSC DS – LPC47N237