View source for ACU Real Time Clock (DIY)

ACU Real Time Clock, DIY from magazine "Amstrad User April 85".

* The RTC 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).

== 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 / Test (W)
  1  Seconds 1/10s Fraction (0..9) (R)
  2  Seconds LSB (0..9) (R)
  3  Seconds MSB (0..5) (R)
  4  Minutes LSB (0..9) (R/W)
  5  Minutes MSB (0..5) (R/W)
  6  Hours LSB (0..9) (R/W)
  7  Hours MSB (0..2) (R/W)
  8  Day LSB (0..9) (R/W)
  9  Day MSB (0..3) (R/W)
  A  Day of Week (1..7) (R/W)
  B  Month LSB (0..9) (R/W)
  C  Month MSB (0..1) (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.

== Article ==

<gallery>
image:Amstrad Computer User8504 078.jpg
image:Amstrad Computer User8504 079.jpg
image:Amstrad Computer User8504 080.jpg
image:Amstrad Computer User8504 081.jpg
</gallery>

Observe that the part number, MM58147, in the headline is wrong (it's meant to be MM58174).

[[Category:Hardware]] [[Category:Peripherals]] [[Category:DIY]]