UPSD3422 datasheet(119/293 Pages) STMICROELECTRONICS

119 / 293 page

uPSD34xx

I2C interface

119/293

23.6

General call address

A General Call (GC) occurs when a Master-Transmitter initiates a transfer containing a

Slave address of 0000000b, and the R/W bit is logic 0. All Slave devices capable of

responding to this broadcast message will acknowledge the GC simultaneously and then

behave as a Slave-Receiver. The next byte transmitted by the Master will be accepted and

acknowledged by all Slaves capable of handling the special data bytes. A Slave that cannot

handle one of these data bytes must ignore it by not acknowledging it. The I2C specification

lists the possible meanings of the special bytes that follow the first GC address byte, and the

actions to be taken by the Slave device(s) upon receiving them. A common use of the GC by

a Master is to dynamically assign device addresses to Slave devices on the bus capable of a

programmable device address.

The uPSD34xx can generate a GC as a Master-Transmitter, and it can receive a GC as a

Slave. When receiving a GC address (00h), an interrupt will be generated so firmware may

respond to the special GC data bytes if desired.

23.7

Serial I/O engine (SIOE)

At the heart of the I2C interface is the hardware SIOE, shown in Figure 43. The SIOE

automatically handles low-level I2C bus protocol (data shifting, handshaking, arbitration,

clock generation and synchronization) and it is controlled and monitored by five SFRs.

The five SFRs shown in Figure 43 are:

●

S1CON - Interface Control (Table 54 on page 121)

●

S1STA - Interface Status (Table 56 on page 123)

●

S1DAT - Data Shift Register (Table 57 on page 124)

●

S1ADR - Device Address (Table 58 on page 124)

●

S1SETUP - Sampling Rate (Table 59 on page 125)

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