-Given the lack of [documentation](reference/cm5.pdf) (or, more likely, my lack
-of understanding it) I can only *assume* the CM-5 monitor operates at a 5V TTL
-level. This would of course be an issue since the Pico operates at 3.3V and
-would explain why I was unable to test the code simply by plugging the Pico
-directly into the monitor. It would seem we need a way of boosting the TTL level
-of the Pico---perhaps with some special IC---before we're able to test the PIO
-code.
+Given the lack of
+[documentation](https://www.manualslib.com/manual/3309783/Tandy-Cm-5.html) (or,
+more likely, my lack of understanding it) I can only *assume* the CM-5 monitor
+operates at a 5V TTL level. This would of course be an issue since the Pico
+operates at 3.3V and would explain why I was unable to test the code simply by
+plugging the Pico directly into the monitor. It would seem we need a way of
+boosting the TTL level of the Pico---perhaps with some special IC---before we're
+able to test the PIO code.