MCF548x Reference Manual, Rev. 3
27-8 Freescale Semiconductor

an SPI master, the DTFR[CTAS] field in the command portion of the Tx FIFO entry selects which of the

DCTAR registers is used.

In slave mode, a subset of the bitfields in only the DCTAR0 registers are used to set the slave transfer

attributes. See the individual bit descriptions of this register for details on which bits are used in slave

modes.

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
R 0 TRSZ CPOL CPHA LSBFE PCSSCK PASC PDT PBR
W
Reset0111100 0 00000000
1514131211109 8 76543210
R CSSCK ASC DT BR
W
Reset0000000 0 00000000
Reg
Addr
MBAR + 0x8A0C (DCTAR0), 0x8A10 (DCTAR1), 0x8A14 (DCTAR2), 0x8A18 (DCTAR3),
0x8A1C (DCTAR4), 0x8A20 (DCTAR5), 0x8A24 (DCTAR6), 0x8A28 (DCTAR7)

Figure 27-4. DSPI Clock and Transfer Attributes Register (DCTARn)

Table 27-5. DCTAR Field Descriptions

Bits Name Description
31 Reserved, should be cleared.
30–27 TRSZ Transfer size. Selects the number of bits transferred per frame. The TRSZ field is used in master
mode and slave mode. Table 27-6 lists the transfer sizes.
26 CPOL Clock polarity. Selects the inactive state of the clock (DSPISCK). This bit is used in both master and
slave mode. For successful communication between serial devices, the devices must have identical
clock polarities. As explained in Section 27.7.4.5, “Continuous Selection Format,” switching between
clock polarities without stopping the DSPI can cause errors in the transfer due to the peripheral
device interpreting the switch of clock polarity as a valid clock edge.
0 The inactive state of DSPISCK is low
1 The inactive state of DSPISCK is high
25 CPHA Clock phase. The CPHA bit selects which edge of DSPISCK causes data to change and which edge
causes data to be captured. This bit is used in both master and slave mode. For successful
communication between serial devices, the devices must have identical clock phase settings.
0 Data is captured on the leading edge of DSPISCK and changed on the following edge
1 Data is changed on the leading edge of DSPISCK and captured on the following edge
24 LSBFE LSB first enable. Selects if the LSB or MSB of the frame is transferred first. This bit is only used in
master mode.
0 Data is transferred MSB first
1 Data is transferred LSB first
23–22 PCSSCK CS to SCK delay prescaler. The PCSSCK field selects the prescaler value for the delay between
assertion of DSPICS and the first edge of the DSPISCK. This field is only used in master mode.
00 1 clock DSPICS to DSPISCK delay prescaler
01 3 clock DSPICS to DSPISCK delay prescaler
10 5 clock DSPICS to DSPISCK delay prescaler
11 7 clock DSPICS to DSPISCK delay prescaler