Browse Prior Art Database

Circuit for Programmable Option Select Register that Configures Chip I/O Pins

IP.com Disclosure Number: IPCOM000113449D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Clarke, G: AUTHOR [+2]

Abstract

Disclosed is a circuit that allows a chip to be configured to be truly multi-purpose. Chips used in Personal Computer families such as PS/2, PS/1, etc. often have applications in numerous system types, which have a multitude of functional requirements. Hence means to configure the chip in accordance with its current environment were developed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 64% of the total text.

Circuit for Programmable Option Select Register that Configures Chip
I/O Pins

      Disclosed is a circuit that allows a chip to be configured to
be truly multi-purpose.  Chips used in Personal Computer families
such as PS/2, PS/1, etc. often have applications in numerous system
types, which have a multitude of functional requirements.  Hence
means to configure the chip in accordance with its current
environment were developed.

      The Figure shows an example of two functions controlled by a
register that is programmed during the power up sequence.  The method
described is to assign dual purpose to two pins, controlled via a bit
in a POS (Programmable Option Select) register (5).

      Upon power-on-reset bit 2 in POS register 104 (5) is set high.
Hence -DSP_INT/+NOVRAM CS1 functions as an input, and
+DSP_INTR/+NOVRAM_CS2 is an output driving the system's Digital
Signal Processor (DSP).  -DSP_INT/+NOVRAM_CSI is connected to
bidirectional buffer (2), which is configured as an input, and passes
the input to AND (1).  The non-inverting input of AND (1) is high;
thus if -DSP_INT is low, +DSP_INT_IN goes high.  At the same time
selector (3) passes +DSP_INTR_OUT to the input of Output Buffer (4).
If a system is designed to use the DSP, it is already set up properly
and no further programming is necessary.

      If NOVRAM support logic is required, the setup software must
now write to POS register 94 (not shown) and set bit 7 to zero, thus
allowing acces...