SYNCHRONOUS SERIAL I/O (SSIO) PORT

slave transmitter, it pulls the clock low when the buffer is empty and floats the clock signal when the buffer is full. When the SSIO channel is configured as a slave receiver, it pulls the clock low when the buffer is full and floats the clock signal when the buffer is empty. Figure 9-6 shows the relationship between the serial clock signal (SCx) and the serial data signal (SDx) for handshaking transfers.

	1	2	3	4	5	6	7	8
SCx
idle state = high
sampling edge = falling
shift edge = rising
SDx	D7	D6	D5	D4	D3	D2	D1	D0
(for receptions)
SDx	D7	D6	D5	D4	D3	D2	D1	D0
(for transmissions)

A4331-01

Figure 9-6. Relationship Between Clock and Data Signals (Handshaking Transfers)

9.4PROGRAMMING THE SSIO PORT

In order to program the SSIO port, you must configure the SSIO port pins and registers. At the end of a transfer, the SSIO generates an interrupt request. Enabling the interrupt allows you to use interrupt service or PTS microcode routines to configure and initiate subsequent transfers. The following sections discuss configuring the SSIO port pins and registers and enabling the SSIO interrupts.

9.4.1Configuring the SSIO Port Pins

Before you can use the SSIO port, you must configure the necessary port 10 pins to serve as SSIO signals. For the different SSIO configurations, Table 9-3 lists the SSIO signal types and the corresponding port register settings. See Table 9-1 on page 9-5 and Table 9-2 on page 9-6 for descriptions of the SSIO signals and port registers.

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