Data port selection
First Claim
1. Apparatus for selecting one of a plurality of parallel data ports and for transferring data between the one port and a serial data path, the apparatus comprising:
- (a) a first shift register having a serial data input coupled to the serial data path and having a parallel output;
(b) at least one respective further shift register for coupling with a respective one of the parallel data ports and having a respective serial data terminal coupled to the serial data path and having a plurality of stages, the serial data terminal being one of an input and an output, according to whether the further shift register is for coupling with an output or an input parallel data port, respectively;
(c) a plurality of respective means for coupling the stages of said at least one further shift register to the plurality of parallel data ports, there being one respective means for coupling for each of the plurality of parallel data ports and each of said respective means for coupling having a respective enable control input;
(d) further means for coupling the parallel output of the first shift register to the enable control inputs of the respective means for coupling; and
(e) means for enabling said further means for coupling to select and enable one of said respective means for coupling, that corresponds to the one port, according to contents of the first shift register.
1 Assignment
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Accused Products
Abstract
In order, for example, to expand the input and output of a microcomputer (7) having a serial input/output capability, a parallel data input port (2 or 3) or output port (4 or 5) is selected by clocking serial selection bits from a serial data line (1) into a first shift register (56) and then enabling a latch (58) for the register parallel output (57). This results in a change in level on a particular one of a set of a parallel output lines (35,36,49,50) which corresponds to the particular group of selection bits written, and hence to a particular port. If the selected port is an output port the change in level results in the strobing of a latch (43 or 44) corresponding to that port, and hence the transfer of the contents of a further shift register (39 or 40) corresponding to that port. These contents are previously written in from the serial data path (1), each further shift register (39,40) being connected in cascade with the first register. If the selected port is an input port the change in level results in the enabling of a gate (31 or 32) corresponding to that port, and hence to the transfer of the port information to a shift register (27 or 28) corresponding to that port, whence it is subsequently clocked out to the serial data path via a respective transistor (25 or 26).
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Citations
23 Claims
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1. Apparatus for selecting one of a plurality of parallel data ports and for transferring data between the one port and a serial data path, the apparatus comprising:
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(a) a first shift register having a serial data input coupled to the serial data path and having a parallel output; (b) at least one respective further shift register for coupling with a respective one of the parallel data ports and having a respective serial data terminal coupled to the serial data path and having a plurality of stages, the serial data terminal being one of an input and an output, according to whether the further shift register is for coupling with an output or an input parallel data port, respectively; (c) a plurality of respective means for coupling the stages of said at least one further shift register to the plurality of parallel data ports, there being one respective means for coupling for each of the plurality of parallel data ports and each of said respective means for coupling having a respective enable control input; (d) further means for coupling the parallel output of the first shift register to the enable control inputs of the respective means for coupling; and (e) means for enabling said further means for coupling to select and enable one of said respective means for coupling, that corresponds to the one port, according to contents of the first shift register. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for selecting one of a plurality of parallel data ports for the purpose of transferring data between the one parallel port and a serial data path, the method comprising the steps of:
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(a) transmitting a serial train of selection bits, which identify the one port on the serial data path, to a serial data input of a first shift register; (b) storing the selection bits in the first shift register; (c) first enabling couplings from a parallel data output of said first shift register; and (d) as a result of said first enabling, second enabling at least one control input of respective further couplings, which further couplings couple the plurality of parallel data ports to stages of at least one further shift register, which further shift register has a serial data terminal coupled with the serial data path, the serial data terminal being one of an input and an output, according to whether a respective data port is an output or an input, respectively, so that the one port is coupled to the serial data path. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. Apparatus for selecting one port from a plurality of parallel data ports (2, 3, 4, 5) and for transferring data between the one port and a serial data path, the apparatus comprising:
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(a) a first shift register (56) having a serial data input coupled to the serial data path; (b) a plurality of respective first means for coupling (31, 32, 43/45, 44/46), one of each of the parallel data ports, each having a respective control input, the plurality of first means for coupling comprising; (i) for each of the parallel data ports which is an input port, a respective gate with an enable control input; and (ii) for each of the parallel data ports which is an output port, a respective cascade of a respective latch and a respective buffer, each respective latch having a strobe signal input, each respective buffer having an output enable signal input; (c) a plurality of further respective shift registers (27, 28, 39,
40), one for each of the plurality of parallel data ports, each of the further shift registers having;(i) a respective serial data terminal (21, 22, 23,
24), comprising;(A) a respective input, for each further shift register coupled with one of the parallel data ports which is an output port, or (B) a respective output for each further shift register coupled with one of the parallel data ports which is an input port, which terminal is coupled to the serial data path; and (ii) a respective plurality of stages coupled with the respective data port via the respective first means for coupling; (d) means (14) for clocking each of the first and further shift registers, so that for each output port, the first and respective further shift registers are cascaded with a common clock; (e) second means for coupling a parallel output (35, 36, 49,
50) of the first shift register to the respective control inputs of the plurality of first means for coupling; and(f) means for enabling the second means for coupling to select and enable one of the first means for coupling, which one of the first means for enabling corresponds to the one parallel data port, and which selecting and enabling is on the basis of the contents of the first shift register.
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Specification