CYB-P51/104 Proto Board

The CYB-P51/104 Prototyping Board supports the P51 interface to the PC/104 bus and provides wire-wrap posts at the I/O ports of the 8051. While adhering to the PC/104 format, almost half the board is wire-wrap area for customization. All components, except the P-51, are through-hole for easy probing and replacement of parts.

[CYB-P51/104 Board Photo]
  • The board provides an oscillator circuit for the P-51, although a crystal circuit may be substituted in the wire-wrap area by picking up Xtal1 and Xtal2 at pads under the Oscillator pattern (X1,X2). The Oscillator must be a 3.3v component, as required by the P-51. See the clock circuits in the user manual for support components for a crystal circuit.
  • An external pushbutton switch (SW1) can be used to manually reset the P-51 while in an active PC/104 slot. The host software must release this hard reset of the P-51 (see P-51 Code RAM in manual).
  • The base address from the PC/104 host is switch selectable on a DIP-switch that is accessible at the edge of the board. See the table below for switch settings. The required IRQ is software selectable.
  • On-board Voltage regulator provides 3.3 volts to the P-51 and oscillator using the computer system's 5-volt supply. The P-51 I/O pins drive 3.3 volts and are 5-volt tolerant.
  • All of the relevant PC/104-bus signals are brought to the elevated socket at the bottom of the board. Alternatively, a micro-controller host could interface to the P-51 at the same interconnect posts.
  • The four 8-bit 8051 I/O ports of the P-51 are brought to wire-wrap posts at W3.
  • Of the remaining dedicated 8051 signals, X1 and X2 are available at the Oscillator circuit, Reset is replaced by ResetDrv from the PC/104-bus, and EA and PSEN are not implemented in the P-51.
  • The remaining P-51 signals, CE_out, ALE, and Clk_Out are available on W3, and CE and ALI are hardwired near C6. CE is tied low and ALI is pulled high.
  • As a convenience to your application, eight LEDs, buffered through a 74HCT244, are provided. Wire-wrap posts at W4 connect to the inputs of the buffer and W5 connects to the outputs. The buffer and LEDs are 5v components.
  • An RJ-45 jack pattern allows eight signals to be brought off-board. Alternatively, a wire-wrap grid is also available at that location.
  • System power may be accessed at W1.
  • A power indicator LED is connected to 5v.
Noise issues and considerations:

As a matter of good design practice, the signals from the P-51 should not be driven off-board without buffering, and should be protected from noisy circuitry. Your low-noise digital circuitry should be added to the on-board wire-wrap area, rather than cabling to a neighboring board. Noisy circuitry should be separated and buffered from the 3-volt area. Your production design should include a ground plane with a good grounding connection to all eight P-51 ground pins.

Base Address Switch Settings:

All Closed000000
All Open 1111EC


[CYB-P51/104 Circuit]