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MC6809 board and shields


I just made 4 more PCB designs in the series described a few weeks ago for the MC6800:

The new boards are:
- MC6809 CPU, with (EE)PROM, RAM, and MC6821 GPIO.
- A 'shield' for up to eight DLG7137 alpha-numeric displays. Includes a 555 timer that can optionally interrupt the CPU periodically to cause a display update.
- A 'shield' for up to ten 7-segment LED displays. Has the same 555 feature as above.
- A 'shield' for playing with audio sound effects and such. Includes an AY-3-8912 sound chip (used in some vintage arcade games), and a pair of ISD2560 recorder/player chips. Also an LM386 amp for audio output. Also an MC6850 UART that can run at 31.25 Kbaud to act as a MIDI interface.

Today I tested the first two boards, and all is working so far. Pictures and schematics attached.
The extra 2KB memory chip position on the 6809 board is set up to support either RAM or EEPROM (so that the 6809 can have non-volatile memory).


I messed up on posting one of the pix - here it is:

Today I finished "board bring-up" on another shield, driven by the new 6809 board.
It is an "audio sound effects" board, based on an AY-3-8912 sound chip, plus a pair of ISD2560 audio sampling chips.
I had to make several changes to make everything work right. The attached schematic includes those changes.
The ISD datasheet is missing a couple of details - most importantly, when a playback is triggered, there is ~25mS delay before it actually outputs the sound. The datasheet has a timing diagram that indicates there is NO delay.
Questions welcome!


I seem to have trouble doing multiple attachments correctly.
Here's the schematic.


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