Renesas SH7781 - Manual (Page 1365)

26. Serial Sound Interface (SSI) Module
Rev.1.00 Jan. 10, 2008 Page 1335 of 1658
REJ09B0261-0100
26.5 Usage Note
26.5.1 Restrictions when an Overflow Occurs during Receive DMA Operation
If an overflow occurs during receive DMA operation, the module must be reactivated.
The receive buffer of SSI has 32-bit common register to the left channel and right channel. If an
overflow occurs under the condition of control register (SSICR) data-word length (DWL2 to 0) is
32-bit and system-word length (SWL2 to 0) is 32-bit, SSI has received the data at right channel
that should be received at left channel.
If an overflow occurrence is confirmed through an overflow error interrupt or overflow error status
flag (the OIRQ bit in SSISR), disable the DMA transfer of the SSI to halt its operation by writing
0 to the EN bit and DMEN bit in SSICR (then terminate the DMAC setting). And clear the
overflow status flag by writing 0 to the OIRQ bit, set the DMA again to restart transfer.
26.5.2 Pin Function Setting for the SSI Module
Before setting or activating the SSI module, set the peripheral module select registers and the port
control registers in terms of the SSI0 and SSI1 channels as described in section 28, General
Purpose I/O Ports (GPIO).
26.5.3 Usage Note in Slave Mode
When terminating data transmission in slave mode, the WS signal (SSI WS) input should be kept
the active state until SSICR.IDST becomes 1 after SSICR.EN is cleared to 0 (see next page
figure). The “active state” means the WS signal is being input high (or low) and low (or high)
alternately as for each system word cycles (it will become more than five system word cycles after
EN bit is cleared to 0).
If the WS signal active state input is stopped before SSICR.IDST becomes 1, the transfer of the
SSI is not terminated normally and the transfer will be suspended. If SSICR.EN is set to 1 again in
this state, the transfer is resumed from the suspended state and an unexpected data transfer may
occur.
Note that, the normal data transmission of the SSI can be resumed from the first or second WS
falling edge after the EN bit is set to 1 while the IDST bit is 1.