5-10 Operating Registers
determines the transfer rate. For example,if SCLK is
40 MHz and the SCF value is set to divide byone, then
the maximum synchronous receive rate is 10 Mbytes/s
((40/1) /4 = 10).
For synchronous send, the output of this divider gets
divided by the transfer period (XFERP) bits in the SCSI
Transfer(SXFER) register, and that value determines the
transfer rate. For validcombinations of the SCF and
XFERP,see Table 5.2.
Note: For additional information on howthe synchronous transfer
rateis deter mined, Section 2.6.3, “Synchronous Operation,”
page 2-13.
R Reserved 3
CCF[2:0] Clock Conversion Factor [2:0]
These bits select the frequency of the SCLK for
asynchronous SCSI operations. The bit encoding is
displayed in Table5.2. All other combinations are
reserved.
Table 5.1 Synchronous Clock Conversion Factor
SCF2 SCF1 SCF0 Factor Frequency
0 0 0 SCLK/3
0 0 1 SCLK/1
0 1 0 SCLK/1.5
0 1 1 SCLK/2
1 0 0 SCLK/3
1 0 1 Reserved
1 1 0 Reserved
1 1 1 Reserved