ACU Real Time Clock, DIY from magazine "Amstrad User April 85".
== Technical ==
Uses a Z80 PIO, MM58174 RTC, 6116 (2K RAM), 32.768kHz Crystal. Both RTC and RAM are backed by rechargeable 3.6V NiCad battery. Used I/O Ports are (with only A10,A4,A3 decoded):
FBE7 Z80 PIO Data In/Out Port A
FBEF Z80 PIO Data In/Out Port B
FBF7 Z80 PIO Configure Port A
FBFF Z80 PIO Configure Port A
The 4bit RTC Registers are:
0 Not used
1 Seconds Fraction (R)
2 Seconds LSB (0..9) (R)
3 Seconds MSB (0..5) (R)
4 Minutes LSB (R/W)
5 Minutes MSB (R/W)
6 Hours LSB (R/W)
7 Hours MSB (R/W)
8 Day LSB (R/W)
9 Day MSB (R/W)
A Day of Week (R/W)
B Month LSB (R/W)
C Month MSB (R/W)
D Leap Year Shift Register (W)
E Stop/Start (W)
F Interrupt (R/W)
Registers 1..C are BCD (range 0..9), a value of 0Fh in these registers indicates Failure.
The chip doesn't include a Year register (aside from the leap-year shift register, but it can span only 4 years, and it is write-only).
== Article ==
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[[Category:Hardware]] [[Category:Peripherals]] [[Category:DIY]]