Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 17)

AN93
Rev. 1.3 17
2.2. System Interface
The ISOmodem can be connected to a host processor through a UART, SPI or parallel interface. Connection to the
chip requires low-voltage CMOS signal levels from the host and any other circuitry interfacing directly. The
following sections describe the digital interface options in detail.
2.2.1. Interface Selection
The interface is selected during reset, as described in "2.1. Resetting the Device". Tables 12, 13, and 14 show the
functions of the affected pins for possible interface modes for 16-, 24- and 38-pin packages, respectively.
Table 12. Pin Functions vs. Interface Mode (SOIC-16)
Pin # UART Mode SPI Mode
3 RI RI
5 RXD MISO
6 TXD MOSI
7 CTS SCLK
11 INT INT
14 ESC ESC
15 DCD DCD
16 RTS SS
Table 13. Pin Functions vs. Interface Mode (TSSOP-24)
Pin # UART Mode SPI Mode Parallel Mode
2 FSYNC (SSI) FSYNC (SSI) D6
3 CLKOUT (SSI) CLKOUT (SSI) A0
8 RTS SS D7
9 RXD MISO RD
10 TXD MOSI WR
11 CTS SCLK CS
15 AOUT AOUT INT
16 INT INT D0
17 RI RI D1
18 SDI (SSI) SDI (SSI) D2
22 ESC ESC D3
23 DCD DCD D4
24 SDO (SSI) SDO (SSI) D5