Timer1 Gate not working on PIC16F636

[johnl]

A biphase encoder's phase A output is wired to T1CKI (A5) and phase B is wired to T1G (A4). When the shaft rotates clockwise, phase A's rising edge coincides with a high on B, and in the other direction the rising edge coincides with a low on B.

However Timer1 is counting up in both rotation directions.

Timer1 is set up like this:

[Ttelmah]

It would do.
The gate, is just a logic input. Look at the diagram in the data sheet. If the edge has changed, then the gate releases, this will be seen as a count.
The counter only runs in one direction, so both movement directions will just give counts 'up' with your configuration....

Best Wishes

[johnl]

[Ttelmah]

No. You are not reading the data sheet properly. If you look at Fig 6.1, the gate signal is taken, and fed through a programmable inverter (top right corner of the diagram), then logically combined with the enable signal, and feeds into an _and_ gate with the incoming signal. Now, 'yes' the timer counts rising edges, but if the incoming signal is _high_ and the gate signal into the and gate goes 'high', the circuit will generate a rising edge on it's output, which will then be counted. Clock _pulses_ that have occurred, while the gate is off, will be missed, but if the pulse is still active when the gate re-enables, it _will_ be counted. The logic is quite explicit.

Best Wishes

[johnl]

I must be looking at a different Figure 6-1 diagram. I follow your description until
" into an _and_ gate with the incoming signal."

On my diagram that _and_ gate has TMR1ON for the other input, not the "incoming signal" which I assume you mean "clock signal."


For reference, the diagram is on this page: DS41232D-page 65

[Ttelmah]

Mines an original release 'A' paper data sheet. Nicely shows the and gate immediately to the right of the actual timer counter.
Sounds as if Microchip decided they were telling us too much!....

Best Wishes