EMI is a big problem. Several precausions should be taken to avoid it:
1. make a good and careful PCB design
2. put a small resistor in VCC line at each component causing EMI (10 ohms is OK) (current spikes also emit EMI)
3. put a decoupling capacitor nearby resistor 10 ohms but on the oposite side (not at the VCC pin)
4. put a small choke in 517A VCC line
5. make your software carefully, if possible, take an advantage of a sleep and power down mode.
(in some delays, put 517A into sleep mode while timer is running to wake it up)
In sleep mode, ALE, PSEN and BUS signals are static and so causing no EMI.