Music Machine

From CPCWiki

The Ram Music Machine

Description

A digital sound sampling and playback device. The Music Machine was designed by Flare Technology and manufactured by RAM Electronics.

The Amstrad CPC version is almost identical to the the ZX Spectrum version, only difference was the address decoding logic.

The Music Machine came with a simple microphone. Recording quality could be improved by using a better(and more expensive) microphone. It came with its own sound sampling software and a sequencer.

No known emulator supports the Music Machine. There was a club advertised through the magazine Sinclare User which sent out a computer tape twice a year full of interesting software developed for the Ram Music Machine. This was contributed to by the members and included thing such as a 128k sampler, fsk syncing mods to the original software and many useful midi tools to name but a few.

The Music Machine was never used for producing sound effects in Demos.

Technical Specifications

Information from the manual:

The Music Machine incoporates two Ferranti devices for digital-to-analogue (DAC) and analogue-tod-digital (A to D) conversion. The part numbers are ZN429E8 and ZN449 respectively. The circuit also include a Motorola 6850 ACIA chip (Asynchronous Communications Interface Adapter) for handling the MIDI channel, two anti-alias filters (one for input and one for output), a discrete microphone amplifier and a headphone amplifier. The clock signal for the ACIA and the ZN449 is provided by a ceramic oscillator.

The incoming signal from the microphone amplifier is sampled to an 8-bit resolution at a rate of 19.444 thousand samples per second. This yields an analogue bandwidth of approximately 9.5KHz which is in fact the cutoff frequency of the filters.

The clock signal for the ACIA is unknown. As said above it is based one the same oscillator as used for the ZN449, however, the oscillator is probably whatever MHz (?) divided by whatever (?), and its unknown if the ACIA and ZN449 clocks are using the same divider (ie. the ZN449 samples at 19.444kHz, but the ACIA may, or may not, use another frequency).

The Music Machine uses NMI interrupt, but it is not clear exactly what it uses it for.

All of the devices on The Music Machine data bus are accessible to the Amstrad within its I/O space. ACIA transactions must use 16-bit IO instructions; the converters are accesible via 8-bit IO instructions.

Port	Direction	Name	Description
F8E8h	Write Only	INTERUPT_SEL	Writing 01 to this port disables internal Amstrad interrupts and replaces the IRQ signal from ACIA. Writing 00 restores normality. (Unclear how this works exactly - the description sounds as if uses an External Interrupt (rather than a NMI), and as if it does somehow disable the CPC's internal 300Hz interrupt?)
F8ECh	Write only	ACIA_Control	See 6850 ACIA chip for details
F8EDh	Write only	ACIA_Data_write	See 6850 ACIA chip for details
F8EEh	Read only	ACIA_Status	See 6850 ACIA chip for details
F8EFh	Read only	ACIA_Data_read	See 6850 ACIA chip for details
F8F0h	Write only	DAC_WRITE	Data can written to the DAC via this port
F8F4h	Read only	ADC_READ	The contents of the A-to-D can be read via this port. Note that the A-to-D must have been startet at least 20uS before this port can be read
F8F8h	Strobe	ADC_START	Reading or writing to this port will start analogue to digital conversion