MicroWire Interface
7-38
Set up the DMA, IT, AUTO_TX, and CS_TOGGLE modes in this register.
In DMA mode, a DMA request is initiated each time a transmission slot is
available.
The maximum word size in DMA mode is 16 bits.
Notes:
You cannot use another CS in normal or DMA mode when a DMA mode is
active on one specific CS.
To use the
µ
Wire in DMA transmit mode, DMA_EN and AUTO_TX_EN must
be enabled, and IT_EN is best disabled. The AUTO_TX_EN can be active
when DMA_EN is disabled.
7.4.2
Protocol Description
The serial port must be configured in order to use the setup registers.
This interface can only drive one device at a given time. Therefore, the
chip-select of the selected device must be set to its active level before starting
any read or write process.
After the loading of the transmit data register (TDR), a write process is
activated by setting the START bit to 1 and by writing a value different from zero
to the NB_BITS_WR field.
A read process is always simultaneous with a write process, which means that
at every serial clock (SCLK) cycle data is read. After having finished a write
process (if necessary), a number (defined by NB_BITS_RD) of SCLK cycles
is generated to allow storage of data from the serial input DI.
The transmitted data word is shifted out on the rising or falling edge of the serial
clock (according to the value of the CSx_EDGE_WR bits of the setup regis-
ters). The received data word is shifted in on the falling or rising edge of the
serial clock (according to the value of the CSx_EDGE_RD bits of the setup reg-
isters). When CSx_EDGE_WR and CSx_EDGE_RD bits have the same val-
ue, it is assumed that the device behavior is the one shown in Figure 7–18.
Otherwise, the required behavior of the external device is shown in
Figure 7–19.
