CommTech FASTCOM ESCC-PCI-335, Hardware Reference Manual

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clock run:
setclock.exe 0 32000000
using the following register settings:
MODE = 0x88
CCR0 = 0x98
CCR1 = 0x16
CCR2 = 0x18
CCR3 = 0x00
CCR4 = 0x00
The receive source will be recovered from the data stream. The transmit source will be the BGR/16 output.
Now for the async channel. We are locked into the 32 MHz input clock, so we will try to find a value for N that
gets our desired 38400 bps:
38400 = (32E6/16)/((N+1)*2)
N = 25.04 (we cannot attain non-integer values for N).
If we use N = 25 we would get:
bitrate = (32E6/16)/(25+1)*2 = 38462 bps
If we use N = 26 we would get:
bitrate = (32E6/16)/(26+1)*2 = 37037 bps
Using the closest value and setting the registers to
MODE = 0x08,
CCR0 = 0xC3,
CCR1 = 0x1F,
CCR2 = 0x38,
CCR3 = 0x00,
CCR4 = 0x80, and
BGR = 0x19
will yield an asynchronous data format (with 16X oversampling) at about 38400 bps.
If later you decide that you need to get 115200 bps on the async channel you will find:
115200 = (32E6/16)/((N+1)*2)
N = 7.68
Using N = 7
bitrate = (32E6/16)/((7+1)*2) = 125000 bps
Using N = 8
bitrate = (32E6/16)/((8+1)*2) = 111111 bps
The ideal situation would be to adjust the 32 MHz clock such that the deviation between the desired and actual
rates is spread between both channels (with the DPLL recovering the clock, the actual clock that feeds it is not as
critical as a clock mode that uses the clock directly).
Clock modes 0b, 3b, 4, and 7b are more sensitive to the selected rate in synchronous modes, as there is no
oversampling. The rate you select is the rate you will get, whereas oversampling modes (using the DPLL or
ASYNC BCR) are more tolerant to differences between the rate you set and the rate you want.