Amdrum: Difference between revisions
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== Partial dissassembly of player == | == Partial dissassembly of player == | ||
exx | exx | ||
ld a,(bc) | ld a,(bc) ;get channel 1 | ||
add a,(hl) | add a,(hl) ;add channel 2 | ||
ex de,hl | ex de,hl | ||
add a,(hl) | add a,(hl) ;add channel 3 | ||
inc hl | inc hl | ||
ex de,hl | ex de,hl | ||
inc bc | inc bc | ||
add a,80h | add a,80h ;add bias (signed to unsigned) | ||
inc hl | inc hl | ||
exx | exx | ||
out (c),a | out (c),a ;out [FFxxh] with C=whatever | ||
ld b,0f6h | ld b,0f6h | ||
in a,(c) | in a,(c) | ||
ld c,a | ld c,a ;C=PIO Port C (keyb row, tape, psg control) | ||
xor 05h ;five ??? | xor 05h ;five ??? | ||
out (c),a | out (c),a | ||
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ld (404eh),a | ld (404eh),a | ||
out (c),c | out (c),c | ||
... ;something missing here? | |||
ld b,0ffh | ld b,0ffh | ||
nop | nop | ||
| Line 71: | Line 71: | ||
nop | nop | ||
exx | exx | ||
ld a,(bc) | ld a,(bc) ;get channel 1 | ||
add a,(hl) | add a,(hl) ;add channel 2 | ||
ex de,hl | ex de,hl | ||
add a,(hl) | add a,(hl) ;add channel 3 | ||
inc hl | inc hl | ||
ex de,hl | ex de,hl | ||
inc bc | inc bc | ||
add a,80h | add a,80h ;add bias (signed to unsigned) | ||
inc hl | inc hl | ||
exx | exx | ||
Revision as of 21:18, 13 January 2010
The Amdrum is a 8bit D/A converter (hardware) with drumkit (software), made by the British company Cheetah.
Quality of the playback was nice, considering the time and price.
The samples were read from the suplied tapes.
There were serveral tapes with different themes.
Along with the Amdrum came a sequencing program.
It was possible to copy the samples to disc, but the sequencing program had to be patched!
Amdrum was probably Cheetahs version of the SpecDrum (As revealed on the PCB "AMSTRAD SPECDRUM")
No CPC emulator supports the Amdrum. To hear 'Amdrum' in action the Spectrum emulator Spectaculator emulates the SpecDrum.
No other software than Cheetahs own sequencer is know to use the Amdrum.
Technical Specifications
- Uses I/O Port FFxxh (Write only), ie. only /IORQ, /WR, A15-A8 are decoded. A7..A0 are not decoded, and /RD isn't used, too.
- Port usage: Write 8bit unsigned sample data to Port FFxxh. The D/A converter is mono and has only one channel (mixing multiple channels is to be done by software).
- The Amdrum software uses port FFxxh. Where "xx" is garbage coming from the Amdrums keyboard scanning routine (see disassembly below).
The five chips on the single-sided PCB are:
| 74LS30N | Single 8-input NAND | Port decoding, /ADDR_MATCH=LOW when A8..A15 all HIGH |
| 74LS32N | Quad 2-input OR | Port decoding, /DAC_WRITE when /ADDR_MATCH, /IORQ, /WR all LOW |
| SN74LS04N | Hex Inverters | purpose unknown? (used in the analog part, not for Port decoding) |
| TL064CDP | Quad Amplifier | no info how the 4 amplifier stages are used? |
| Ferranti ZN428E-8 | 8bit DAC | mono one-channel 8bit D/A converter (unsigned samples) |
- ZN428 Datasheet - 8bit D/A Converter
- TL064 Datasheet - Quad Amplifier
Partial dissassembly of player
exx ld a,(bc) ;get channel 1 add a,(hl) ;add channel 2 ex de,hl add a,(hl) ;add channel 3 inc hl ex de,hl inc bc add a,80h ;add bias (signed to unsigned) inc hl exx out (c),a ;out [FFxxh] with C=whatever ld b,0f6h in a,(c) ld c,a ;C=PIO Port C (keyb row, tape, psg control) xor 05h ;five ??? out (c),a ld a,0f4h in a,(66h) ld (404eh),a out (c),c ... ;something missing here? ld b,0ffh nop nop nop exx ld a,(bc) ;get channel 1 add a,(hl) ;add channel 2 ex de,hl add a,(hl) ;add channel 3 inc hl ex de,hl inc bc add a,80h ;add bias (signed to unsigned) inc hl exx out (c),a ;out [FFxxh] with xx=garbage (above PIO Port C value)
Kits
Afro Kit Covertape
- Afro Kit Covertape - Instructions
-
Afro Kit Covertape
-
Afro Kit Instructions
-
Afro Kit Errata
Electro Kit Covertape
- Electro Kit Covertape - Instructions
-
Electro Kit Covertape
-
Electro Kit Instructions
Latin Kit Covertape
- Latin Kit Covertape - Instructions
-
Latin Kit Covertape
-
Latin Kit Instructions
Tapes
Amdrum Tape
- Amdrum Tape
-
Amdrum Tape side A
-
Amdrum Tape side B
Afro Kit Tape
- Afro Kit Tape
-
Afro Kit Tape side A
-
Afro Kit Tape side B
Electro Kit Tape
- Electro Kit Tape
-
Electro Kit Tape side A
-
Electro Kit Tape side B
Latin Kit Tape
- Latin Kit Tape
-
Latin Kit Tape side A
-
Latin Kit Tape side B
Pictures
- AMDRUM
-
Component side
-
"AMSTRAD SPECDRUM"
-
Screen shot
-
Screen shot
-
Box
-
Amdrum inside box
Manual
- Amdrum Manual (pdf)
Reviews / Commercials
- Commercials for the Amdrum
-
Commercial for Amdrum
-
Review of the Amdrum in Amstrad Computer User
Weblinks
Review of the Spectrum version
Other playback devices
- Digiblaster (DIY) (8bit DAC on printer port)
- Music Machine
Videos
AmDrum on Amstrad CPC (emulated with JavaCPC)
{{#ev:youtube|0z-jGDOzwGQ|400}}
A presentation(from around 1985) of the ZX Spectrum version of the Amdrum(Specdrum), also mention of the upcomming Amstrad CPC version
{{#ev:youtube|m6R_W9CZWGU|400}}
Download
- Amdrum.zip (CDT for Emulators)
- Amdrum Afro Kit.zip (CDT for Emulators)
- Amdrum Electro Kit.zip (CDT for Emulators)
- Amdrum Latin Kit.zip (CDT for Emulators)