Claims
- 1. In a programmable controller including microaddress control logic, a memory, and microinstruction decoder logic; an improved microaddress control logic circuit comprising:
- a branch control logic responsive to at least a portion of an internal field of a microinstruction word, said branch control logic being operative to develop branch control signals;
- a loop counter coupled to said branch control logic and responsive to a number of said branch control signals, said loop counter being operative to develop a loop count signal;
- a program counter coupled to said branch control logic and responsive to a number of said branch control signals, said program counter being operative to develop a program count signal; and
- stack means coupled to said loop counter and said program counter for selectively storing outputs thereof, said stack means being operative to develop a stack output signal,
- wherein said stack means includes a stack multiplexer, a stack pointer coupled to outputs of said stack multiplexer, and stack memory addressed by said stack pointer.
- 2. A microaddress control logic circuit as recited in claim 1 wherein said loop counter includes a counter multiplexer having inputs coupled to a number of said branch control signals; and a counter register coupled to outputs of said loop counter multiplexer, said counter register developing said loop count signal.
- 3. A microaddress control logic circuit as recited in claim 2 wherein said loop counter further includes a decrementer coupled to said counter register for developing a decremented count signal from said loop count signal, where said decremented count signal is coupled to inputs of said counter multiplexer.
- 4. A microaddress control logic circuit as recited in claim 2 further comprising a zero detector responsive to said loop count signal and operative to develop a zero detection signal therefrom.
- 5. A microaddress control logic circuit as recited in claim 2 wherein said counter multiplexer has inputs coupled to said stack means.
- 6. A microaddress control logic circuit as recited in claim 1 wherein said program counter includes a program counter multiplexer, a program counter register coupled to outputs of said program counter multiplexer for developing said program count signal, and an incrementer coupled to said program counter register and operative to develop an incremented program counter signal from said program counter signal.
- 7. A microaddress control logic circuit as recited in claim 6 wherein said program counter multiplexer has inputs coupled to said branch control logic, said stack means, said program counter register, and said incrementer.
- 8. A microaddress control logic circuit as recited in claim 1, wherein said stack means is further coupled to said branch control logic and is responsive to at least one of said branch control signals.
- 9. A microaddress control logic circuit as recited in claim 1 wherein said stack multiplexer has inputs coupled to said branch control logic, said program counter, and to said loop counter.
Parent Case Info
This application is a division of application Ser. No. 07,370,148, filed Jun. 21, 1989, now U.S. Pat. No. 5,179,716, which is a continuation of application Ser. No. 06/881,143, filed Jul. 2, 1986, now abandoned.
US Referenced Citations (5)
Divisions (1)
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370148 |
Jun 1989 |
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Continuations (1)
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881143 |
Jul 1986 |
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