ACU Real Time Clock, DIY from magazine "[[Amstrad Computer User |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 RAM2Kx8bit SRAM), 4040 (12bit counter for sequential SRAM addressing), and 32.768kHz Crystal(for the RTC). Both RTC and RAM are backed by rechargeable 3.6V NiCad battery. Used I/O Ports are (with only A10,A4,A3 decoded): FBE7 FBE7h ACU Real Time Clock [[Z80 PIO ]] Data In/Out Port A Bit7..4 SRAM Data7..4 Bit3..0 SRAM Data3..0 and 4bit RTC Data FBEF FBEFh ACU Real Time Clock [[Z80 PIO ]] Data In/Out Port B Bit7 SRAM /CS and /OE (0=Select) Bit6 RTC /CS (0=Select) Bit5 RTC /RD (0=Read) Bit4 RTC /WR (0=Write) Bit3 RTC Address A3 and SRAM /WE (0=Write) Bit2 RTC Address A2 and SRAM Address Counter RST (1=Reset, 0=Active) Bit1 RTC Address A1 Bit0 RTC Address A0 and SRAM Address Counter /CLK (1-to-0=Increment) FBF7 FBF7h ACU Real Time Clock [[Z80 PIO ]] Configure Port A FBFF FBFFh ACU Real Time Clock [[Z80 PIO ]] Configure Port AB
The 4bit RTC Registers are:
0 Not used / Test (W)
C Month MSB (0..1) (R/W)
D Leap Year Shift Register (W)
E Stop/Start (0=Stop and set Seconds to 00.0, 1=Start) (W)
F Interrupt (R/W)
Registers 1..C are BCD (range 0..9), a value of 0Fh in these registers indicates Failure(this may happen if the time changed while reading - if that happens, restart reading ALL time registers).
== Article ==
<gallerycaption="Part 1 - RTC DIY Hardware (ACU April 1985)">
image:Amstrad Computer User8504 078.jpg
image:Amstrad Computer User8504 079.jpg
Observe that the part number, MM58147, in the headline is wrong (it's meant to be MM58174).
[[Category<gallery caption="Part 2 - Software for the RTC (ACU May 1985)">image:Hardware]] ACU8505-008.jpgimage:ACU8505-014.jpgimage:ACU8505-016.jpg</gallery> [[Category:Peripherals]] [[Category:DIY]]