DS1302 Real Time Clock for the RC2014 computer
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README.md

DS1302 Real Time Clock for the RC2014 computer

Picture of the board

The board

RomWBW has code to support a DS1302 Real Time Clock, enabling files to be timestamped and other timekeeping operations. This board implements the clock in a standard way for the RC2014.

What can you use this for?

Telling the time :)

Getting started with RomWBW

Set DSRTCENABLE to true in the configuration and rebuild your ROM image.

On startup you will see the time shown.

Boot

ZSystem has more complete support for time utilities than CP/M. After booting into ZSystem by pressing Z, Run ldds to load the resident time driver. td can then be used to set the time as well as view it.

In CP/M RTC.com can be used for querying and setting the clock but it is very basic.

Jumpers

SW1 - Address configuration. For the default address of 0xC0, set switches 5 and 6 to on.

Bill Of Materials

Reference Value Farnell part no Rapid part no Digi-key part no
P1 1x39 right angled pin header 732-5350-ND
BT1 Keystone 106 20mm battery holder for CR2032 1650672 36-106-ND
BT1 CR2032 battery P189-ND
U1 CD74HCT688E COMPARATOR, SINGLE, PDIP-20 2407104 296-2131-5-ND
U2 SN74HCT125N LOGIC, BUS BUFF TRI-ST QD, 14DIP 1739676 296-8386-5-ND
U3 CD74HCT174E 74HCT CMOS, 74HCT174, DIP16, 5.5V 1105983 296-2100-5-ND
U4 DS1302N+ RTC W/ RAM, 248B, D-D-M-Y, HH:MM:SS, DIP 2515367 DS1302N+-ND
U5 SN74HCT32N IC, QUAD 2-INPUT OR, 74HCT32, DIP14 9591982 296-1615-5-ND
C1-5 0.1uF MLCC capacitor BC2665CT-ND
Y1 32.768 kHz crystal 9712887 535-9034-ND
RN1 10k 8 Pin Commoned Resistor Network 63-0125 4608X-1-103LF-ND
SW1 6 way DIL switch 80-0338 CT2066-ND
U1 CONN IC DIP SOCKET 20POS TIN AE10015-ND
U2 CONN IC DIP SOCKET 14POS TIN AE10012-ND
U3 CONN IC DIP SOCKET 16POS TIN AE10013-ND
U4 CONN IC DIP SOCKET 8POS TIN AE10011-ND
U5 CONN IC DIP SOCKET 14POS TIN AE10012-ND

Construction tips

The footprint for the battery holder is designed for a Keystone 106, other battery holders should work if the pins are ~20.5mm apart, which seems to be fairly standard.