What is it?

This kit, designed around the RP5C01 RTC chip, is part of the Yellow MSX series of modules to give your RC2014 MSX compatibility.

It gives your RC2014 the ability to remember the date and time when power is off.

The RPC501 chip maintains a time/date counter and when the machine is switched off, the chip is powered by a coin CR2032 battery.

In addition to keeping time, it also has a small amount of onboard RAM, that is also powered by the battery when main power is off. This RAM can be used to store machine specific settings, such as boot screen color and mode.

Key Features

• MSX2 compatible Real Time Clock
• Optional Reset on Power signal
• MSX2+ compatible F4 cold/boot register
• Compatible with RomWBW*

* see RomWBW's dev branch

Operation

Detail of building, configuring, calibrating the board can be found on the github project page

Reset on power

To enable this capability, you need to bridge jumper J2 (RESET). Please see the notes on the github project regarding the RC2014 Dual Clock module's Reset on power function.

Calibration

The trimmer capacitor can be use to adjust the onboard clock for calibrating timing accuracy. The MSX-DOS application RTCCALB.COM (downloadable from the github project) can be used to show reference of the RTC to your CPU's clock

Synchronizing with external time using ESP8266 Wifi Module.

It is possible to synchronise the RTC via the ESP8266 to an internet synchronised clock. It requires the WIFI module and SIO/2 be linked via the 2nd serial channel. The ESP8266.COM MSX-DOS application along with custom firmware for the ESP8266 are still under development. See the Hackaday project log for current status.

MSX F4 boot register

This is a single bit register at IO address $F4, that MSX software can use to identified if your machine was cold booted (powered on), or warm booted (reset). MSX Bios software will skip boot screen and other startup code on a warm boot.

What is the 'Yellow MSX Series of Boards'?

These are a series of boards that I am developing to achieve MSX compatibility for RC2014 systems.

The idea is that you can build each board one at a time, test it and play with it under RomWBW - and then once you have the set - load up some MSX/MSX2+ games!

More details are available within the hackaday project

Errata (1.6 revision)

The ceramic capacitor value for the main clock should be 30pf, not 33pf.

With a 33pf, the clock will work but may run a little slow. Decreasing the capacitor's value will make the clock run a little faster.

Individual cases may vary, so the kit has been supplied with 27pf, 30pf and 33pf to allow for experimentation.

What's included in this kit

The full kits includes (PCB, passive components, IC and their sockets, including the RP5C01 chip)

The RP5C01 chip is an obsolete, no longer manufactured component. The chip supplied may be used or new-old-stock. I test each chip prior to shipping.

A battery is not included. Requires a standard coin CR2032 battery.

What else do I need to make this work?

• You need a working RC2014 system (CPU, Clock, etc).
• Enhanced Bus backplane required.
• For MSX operation, you need the other Yellow MSX series for RC2014 modules (PPI/Keyboard, ROM/RAM Memory, V9958 Video)

Disclaimer

Please note that this is a kit, produced by a non-professional (me) for hackers, DIYers' and retro lovers, to tinker with. I will do my best to answer any support questions you may have.

The clock's timing should generally be adequate, but please don't expect super accurate time keeping.

Normally shipped next working day, however during busy periods this may extend slightly.

It is your responsibility to pay any import duty or other taxes where appropriate.

For EU locations:

* Please see Lectronz's Terms and Condititions (https://lectronz.com/pages/terms_and_conditions)

* For order 150 EUR or over, it will be your responsibility to pay any import duty or other taxes where appropriate.

For USA: From Aug 29 2025, new rules are to be enforce.

Package delivery may become impossible for USA destinations. Items may be rejected at point of entry into the country.

https://auspost.com.au/business/shipping/parcels-international/international-post-guide/results/united-states#usa-tariff