9
Chapter 2
2.3.4 Select Clock Source of Timers and Counter
Jumpers JP1, JP2 and JP3 are used to select the clock source of Timer 0,
Timer 1 and Counter 2, respectively. Short the upper two pins of the
jumpers to select an external clock source, or short the lower two pins to
select an internal clock source. However, the internal clock source of
Timer 1 is connected to the output of Timer 0, so shorting the upper two
pins of JP2 results in the cascading of Timer 0 and Timer 1 as a 32-bit
timer.
Table 2.1: Jumper Settings
Names of Jumpers
Function description
JPA0, JPA1: Jumpers for ports A0, A1
JPB0, JPB1: Jumpers for ports B0, B1
JPC0L, JPC1L: Jumpers for low nibble
of ports C0, C1
JPC0H, JPC1H: Jumpers for high nibble
of ports C0, C1
Sets port as an output port
Sets port to be software
configurable as input or
output (default)
JP1: Timer 0
P2: Timer 1
P3: Counter 2
Internal counter clock
source
External counter clock
source (default)
JA1
All ports return to state
held just prior to reset
All ports return to default
states (for software-set
ports) or to output port,
output low (for jumper-set
ports
1
1
1
1
1
1
Summary of Contents for PCI-1751U
Page 1: ...PCI 1751U 48 bit Digital Input Output Card with Universal PCI Bus User Manual ...
Page 5: ...2 CHAPTER 1 General Information ...
Page 9: ...2 CHAPTER 2 Installation ...
Page 15: ...11 Chapter2 2 5 PCI 1751U Block Diagram Figure 2 2 PCI 1751U Block Diagram ...
Page 18: ...PCI 1751U User Manual 14 ...
Page 19: ...2 CHAPTER 3 Operation ...
Page 28: ...PCI 1751U User Manual 24 ...
Page 29: ...2 APPENDIX A Function of 8254 Counter Chip ...