2. Configurable Options
21
Tsi381 Evaluation Board User Manual
60E2000_MA001_03
Integrated Device Technology
www.idt.com
Switch S1 is used to manually set PCI bus modes.
Switches S3 and S4 are used to set the PCI bus external clock frequency. By default the PCI bus clock
source is the Tsi381. The external clock can only be connected to the PCI bus by replacing resistors on
the board. When an external clock source is used, an on-board PLL is used to set the proper bus clock
frequency.
Table 8
contains the clock frequency settings for S3.
Table 7: S1 Settings
Switch
Number
Description
Default
Setting
On/Off Setting
1
M66EN
ON
ON = Connects M66EN to all cards
OFF = Forces M66EN high if S1.2 OFF
2
M66EN
OFF
ON = Forces M66EN to GND
OFF = Disables forcing M66EN to GND
Table 8: S3 Settings
Switch
Number
Description
Default
Setting
On/Off Setting
1
DIV_SEL0
OFF
[FBDIV_SEL1, FBDIV_SEL0, DIV_SEL1, DIV_SEL0]
ON = 1
OFF = 0
0,0,0,0 = x 4
0,0,0,1 = x 3
0,0,1,0 = x 2
0,0,1,1 = x 1
0,1,0,0 = x 5.33
0,1,0,1 = x 4
0,1,1,0 = x 2.667
0,1,1,1 = x 1.33
1,0,0,0 = x 6.667
1,0,0,1 = x 5
1,0,1,0 = x 3.33
1,0,1,1 = x 1.67
1,1,0,0 = x 8
1,1,0,1 = x 6
1,1,1,0 = x 4
1,1,1,1 = x 2
2
DIV_SEL1
OFF
3
FBDIV_
SEL0
OFF
4
FBDIV_
SEL1
OFF
