STMicroelectronics AN1365 Application Note Guidelines for Migrating ST72C254 to ST72F264

About this manual

This document serves as a migration guide for developers moving from the ST72C254 (and related subsets like 104, 215, 216) to the newer ST72F264 microcontroller. It details changes in package compatibility, pinout modifications, and timing differences between the two devices.

The note covers specific technical updates including the addition of an SCI peripheral, changes to ISP pins becoming ICC pins, and modifications to internal blocks such as the Watchdog timer, Clock Security System (CSS), and Phase Locked Loop (PLL). It also outlines register map changes and provides formulas for calculating watchdog timeout durations in the new device.

What's inside

• Feature Overview
• Pinout Compatibility
• Timing Differences
• Cycle Accuracy
• Clock Security System
• Phase Locked Loop
• Watchdog Timings
• Register Map Modifications
• System Integrity Control Register

Specifications

Frequently asked questions

What are the main differences in package compatibility between ST72C254 and ST72F264?

All devices are available in SDIP32 and SO28 packages, but some pins have changed to add the SCI peripheral and move ISP pins.

How does the Watchdog timeout duration differ between the two devices?

The ST72F264 watchdog timeout may vary between minimum and maximum times specified in figures, unlike the exact duration of the ST72C254.

Is the Clock Security System (CSS) backup oscillator available in the ST72F264?

No, the ST72F264 does not have a backup oscillator frequency for the CSS feature.