OXCFU950_07 Datasheet, PDF (56/74 Pages) Oxford Semiconductor – USB/UART multi-function 16-bit PC Card device

OXFORD SEMICONDUCTOR, INC.
The OXCFU950 has the facility to operate at baud-rates up
to 12 Mbps. This is due to the fixed 48-MHz baud rate and
the minimum TCR value of 4.
The table below indicates how the value in the register
corresponds to the number of clock cycles per bit. TCR[3:0]
is used to program the clock. TCR[7:4] are unused and
return 0000 if read.
TCR[3:0]
Clock cycles per bit
0000 to 0011
16
0100 to 1111
4-15
Table 27: TCR Sample Clock Configuration
OXCFU950 DATA SHEET
The use of TCR does not require the device to be in 650 or
950 mode although only drivers that have been written to
take advantage of the 950 mode features are able to
access this register. Writing 0x01 to the TCR will not switch
the device into 1x isochronous mode—this is explained in
the following section. (TCR has no effect in isochronous
mode). If 0x01, 0x10 or 0x11 is written to TCR the device
operates in 16x mode.
Reading TCR always returns the last value that was written
to it irrespective of mode of operation.
Table 28 shows typical UART baud rates and the register
settings which can be used to set them:
TCR
Reg(Bin)
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
0100
CPR
Bits(7:3)
00110
00110
00110
00110
00110
00110
00110
00110
00110
00110
00110
00110
00110
00001
00001
00001
00001
00001
Bits(2:0)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
000
000
000
000
Divisor
DLM (Hex)
90
41
18
0C
06
03
01
00
00
00
00
00
00
00
00
00
00
00
DLL(Hex)
3B
8F
09
04
02
01
80
C0
60
40
30
20
10
08
08
04
02
01
Nominal Baud
Rate
(Bits per sec)
50
110
300
600
1200
2400
4807
9600
19,200
28800
38400
57600
115200
230400
1500000.00
3000000.00
6000000.00
12000000.00
Table 28: Typical Baud Rates and Register Settings to Achieve Them
8.10.4 Alternative Baud Rate Control Registers
Table 18 shows the set of OXCFU950 specific alternative
UART baud rate control registers, which can be used
instead of the standard versions of these registers. They
give the facility to prevent legacy drivers with knowledge of
the 950 UART register set from making incorrect
assumptions about the OXCFU950 crystal frequency and
synthesizing incorrect baud rate values by writing to the
standard DLL, DLM, CPR and TCR registers.
Example
• Write 0xEB to UART Indirect register 0x30 to enable
register access to the alternative register set.
• Write new values into A_CPR (0x34) and A_TCR
(0x35) UART indirect registers.
• Write 0x0C into A_ENABLE (0x31) UART indirect
register to enable the alternative CPR and TCR
registers.
• Write 0x00 to UART Indirect register 0x30 to disable
register access to the alternative register set.
DS-0023 February 2007
External—Free Release
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