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Scientific Solutions ® Inc.

BaseBoard ® HandShake Polarity Select Module

HS Polarity Select Module

Provides complete control over the polarity of handshake signals and attaches directly to the BaseBoard.

Plug In Module - HandShake Polarity Select
The Scientific Solutions HandShake Polarity Select module is an optional module for use with the BaseBoard /  ISA or BaseBoard / PCI digital I/O products.  When used with the BaseBoard / ISA card, the module attaches directly to the PC card in the computer.  When used with the BaseBoard / PCI product, the module is housed in the DeskTop unit.  The BaseBoard / ISA and the BaseBoard / PCI DeskTop unit can each accommodate from 1 to 4 modules. 

Each module provides complete control over the polarity of the Port-C bits that are used as handshake signals when operating the Digital I/O port in mode 1 or mode 2.  The BaseBoard ISA and the BaseBoard PCI cards completely support three modes of operation:
    Mode 0 - Basic Input or Output
    Mode 1 - Strobed I/O
    Mode 2 - BiDirectional Operation

When operating in mode 1 or mode 2, Port A and Port B are used for data, whereas Port C is used for handshake signals.  For example, in mode 1 operation the following handshake signals are provided for Port A and Port B:
C0 INTR-A
C1 IBF-B / OBF-B
C2 STB-B / ACK-B
C3 INTR-B
C4 STB-A / IO
C5 IBF-A / IO
C6 ACK-A / IO
C7 OBF-A / IO


IBF and STB
IBF and STB are used when external equipment is sending data TO the BaseBoard.  These signals allow full handshaking between the BaseBoard and the external equipment so no data is lost and transfers occur at a maximum rate.

IBF is Input Buffer Full.
This is a status signal (output from the BaseBoard) to other equipment that indicates the data buffer for writing data from the external equipment to the BaseBoard is FULL and that no other data can be written at this time.  Without the HS module, the polarity of this signal is such that a HI on this output from the BaseBoard indicates the IBF condition.  With the HS module, you can select the polarity to be either HI or LO.  IBF is set "active" by the STB signal being taken active, i.e. by external equipment "strobing" data into the BaseBoard.  IBF is set "inactive" when the computer reads the data from the BaseBoard, which means that the external equipment can strobe in more data.

STB is Strobe
This is a control signal (input to the BaseBoard) from other equipment that is used to "strobe" (also called latch) data into the BaseBoard.  Without the HS module, the polarity of this signal is such that a LO on this input loads data into the BaseBoard.  With the HS module, you can select the polarity to be either HI or LO.  When STB is active, data is latched into the BaseBoard and the IBF status signal is set "active"

OBF and ACK
OBF and ACK are used when external equipment is getting data FROM the BaseBoard.  These signals allow full handshaking between the BaseBoard and the external equipment so no data is lost and transfers occur at a maximum rate.

OBF is Output Buffer Full.
This is a status signal (output from the BaseBoard) to other equipment that indicates that the data buffer for reading data from the BaseBoard to the external equipment is FULL, which means the external equipment can read the data.  Without the HS module, the polarity of this signal is such that a LO on this output from the BaseBoard  indicates the OBF condition.  With the HS module, you can select the polarity as either HI or LO.  OBF is set "active" when the computer has written data out to the BaseBoard Port (OBF-A for Port-A, OBF-B for Port-B).  OBF is set "inactive" when the external equipment activates the ACK input which indicates that the external equipment has read the data.

ACK is Acknowledge
This is a control signal (input to the BaseBoard) from other equipment that is used to "acknowledge" to the BaseBoard that the external equipment has read the data.  Without the HS module, the polarity of this signal is such that a LO on this input indicates to the BaseBoard that the data has been read.  With the HS module you can select the polarity to be either HI or LO.  When ACK being "active" with make the OBF signal "inactive"

INTR
Intr is a signal that is used internally by the BaseBoard to cause an interrupt, if desired.  This signal also is presented to the external equipment, but normally not used by the external equipment.  However, it is possible that some external equipment may want to use this signal.  Without the HS module, the INTR output will produce a HI to cause an interrupt.  With the HS module, you can select either HI or LO.  Note that changing this polarity does not change the polarity of the signal used on the BaseBoard to cause internal interrupts, but only changes the signal for the external equipment.

AND / OR Capabilities
In addition to the Inverting and Non-Inverting control over the IBF, OBF, STB, ACK, INTR signals; the HS module also has circuitry that lets you "combine" handshake signals. 

For example, you select STB-A to strobe only the Port-A data or to strobe both the Port-A AND the Port-B data.  Likewise, you can select STB-B to strobe only the Port-B data or both the Port-A AND Port-B data.  Or you can configure the HS module so that "either" STB-A OR STB-B will strobe data into either or both ports.

The same is true for the ACK-A / ACK-B signals; the IBF-A / IBF-B signals; and the OBF-A / OBF-B signals.

Configuring the HS Module
The HS module has a logic schematic printed right on the module itself that references the various settings you can make.  This convenient approach means not having to carry around or refer to some other manual in order to configure the card.  Just look at the logic schematic and set jumpers to select the desired configuration.

When shipped from Scientific Solutions, the HS module is configured for straight thru connections of the Port-C signals.    Be sure that you know the direction of Port-C signals for the mode (0, 1 or 2) that you are using and avoid configuring the HS module signals C2, C4 and C6 as   INVERTING / AND   if these are Output instead of Input signals.  If C2, C4 or C6 are programmed as Output signals on the BaseBoard and you are using the INVERTING or AND logic on the HS module for these signals, then you will have the output drivers of the BaseBoard fighting the the output drivers of the HS module, i.e. connected together which can cause damage to the BaseBoard or HS module.  Note that the BaseBoard powers up with all signals configured as INPUTS.




HandShake Polarity Select Module Characteristics
Input Connection
 40 position socket connector
 plugs onto BaseBoard
Output Connection
 40 position pin connector
 with same pin-out as the input connection
HandShake Selection Method
 Jumper block
Port-C voltage levels
 TTL
Port-C source/sink current
Inverting or Non-Inverting Logic
 25ma / 25ma
Port-C source/sink current
AND / OR logic
 0.8ma / 16ma


Environmental Specifications
Operating Temperature -40º to +100º Celsius
Storage Temperature -40º to +125º Celsius
Relative Humidity To 95% non-condensing
Agency Approvals Class A, CE-Mark

Specifications subject to change without notice.

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