CA80-boot module.

Boot

• Replaces EPROM.
• Generates CLK, RESET, and NMI signals.
• During boot, it writes the operating system (e.g., the CA80 monitor) and other software from *.hex files specified in the CA80.TXT file to RAM from the SD card.
• It sets the CA80 system clock (from the DS3231 module).

After RESET, it can perform various functions, such as:

• a UART interface,
• a keyboard emulator controlled by UART or a touch keyboard (MPR121),
• a MIKSID-style debugger,
• and others I've forgotten or haven't thought of yet.

Top

U1, U2, and U3 function as a keyboard emulator - they can be omitted (in which case the IDC26 is also unnecessary). The "Serial" connector is compatible with the Z80 MBC-2. It can be used for AVR programming (Arduino IDE) or connecting a terminal (e.g., uTerm).

Bottom

The SD and RTC module connectors didn't fit on top - sorry.

WARNING!!

Pay attention to the MEMEN signal. The design is based on the Z80-MBC2, so there are consequences. MEMEN is equivalent to RAMCE2. The original design only had one RAM chip, while the RC2014 can have multiple modules with some memory, so this signal must reach each one. I chose PIN 40 (USER4) because it's not present in the original RC, to minimize the risk of conflict with another module. I wasn't aware that backplanes, such as the SC112, have connections for adjacent sockets 40-80. This was the first idea for the IEI-IEO "daisy chain." Because of this, the MEMEN signal can be interrupted. The modules containing memory and CA80-boot should have their USER4 and USER8 pins (40 and 80) shorted and be in adjacent sockets!!!

You can also connect the aforementioned pins to the backplane.

Kbd connector.

Connects SYS I/O and bootloader modules and allows to connect display and keyboard.

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