GAL16V8 macrocell control signals Within a GAL16V8 output macrocell, which internal multiplexer controls the enable input of the tri-state output buffer (i.e., determines when the output pin is driven versus placed in high impedance)?

Introduction / Context: The GAL16V8 is a classic simple PLD whose output macrocells provide substantial flexibility: combinational or registered mode, selectable feedback, output polarity, and controlled tri-stating. Correctly identifying which internal multiplexer configures each behavior is key when reading datasheets or fitting logic equations.

Given Data / Assumptions:

• The device includes several named multiplexers: PTMUX (product-term selection), OMUX (output/registered path selection), FMUX (feedback source to the input matrix), and TSMUX (tri-state control selection).
• The tri-state buffer enable (OE control) determines when the I/O pin actively drives versus enters high-Z.
• We assume the standard macrocell organization used in GAL16V8 documentation.

Concept / Approach: Each GAL16V8 macrocell uses a set of multiplexers to choose sources for its internal signals. The TSMUX is specifically dedicated to selecting the source that drives the output-enable path, thereby enabling or disabling the tri-state buffer. This may be tied to a product term, a dedicated OE pin, or another internal control depending on design configuration.

Step-by-Step Solution:

Verification / Alternative check: Check a GAL16V8 macrocell block diagram; you will see the tri-state control line selected by a multiplexer typically labeled TSMUX (or equivalent naming) feeding the OE of the output buffer.

Why Other Options Are Wrong: FMUX selects the feedback path into the input matrix, not the OE. OMUX chooses between registered and combinational outputs, not the tri-state control. PTMUX selects the product term input to a function block, not OE control source.

Common Pitfalls: Confusing OMUX with TSMUX because both influence the output pin’s behavior. OMUX affects what data is presented to the pin; TSMUX affects whether the pin actively drives.

Final Answer: TSMUX