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.

• 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:

	Switch Setting 1234	Seg Addr
All Closed	0000	00
	0001	A4
	0010	AB
	0011	AC
	0100	B0
	0101	B4
	0110	C8
	0111	CC
	1000	D0
	1001	D4
	1010	D8
	1011	DC
	1100	E0
	1101	E4
	1110	E8
All Open	1111	EC

Schematic