LPC47N237-MD datasheet(82/138 Pages) SMSC

82 / 138 page

3.3v I/O Controller for Port Replicators and Docking Stations

Revision 0.3 (10-26-04)

Page 82

SMSC DS – LPC47N237

DATASHEET

15.1.10 SMBus Alert Response

The LPC47N237 does not implement the nSMBALERT response.

15.2

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. The selection allows for the two SMBus devices to be disconnected,

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.

LPC47N237-MD Datenblatt(PDF) 82 Page - SMSC Corporation