8 May
2007
8 May
'07
3:25 p.m.
Jules Richardson wrote:
In a traditional CPU-driven environment the logical
thing to do would
perhaps have been to make the CPU and floppy interface a separate board
to the one containing the interface, with the CPU bus coupling them
together. That way the core stays the same but the interface can change
(USB, SCSI, Ethernet etc.) relatively easily (plug in the right board,
drop in the right firmware ROM).
The reader IS separate from the microcontroller.
The CPLD handles data read, data write, and write gating. Its interface to the
microcontroller consists of three address lines, an 8-bit bidirectional data
bus, a read line and a write line. It's basically the same as the Z80 bus -
nIOR, nIOW, address and data.
The PIC handles the interface between the USB bus and the CPLD (register
programming, waiting for operations to complete, etc), the status LEDs, and
the floppy drive control lines (MOTEN, DS0, DS1, TG42, etc). That
microcontroller and its support circuitry can be torn out and replaced with
close to anything that can be made to speak 8080-style bus protocols (which
usually involves a small amount of glue and not much else).
So if you don't like USB, you're quite welcome to use SCSI, RS232, CAN,
LINBUS, SB-Bus, Firewire, or some form of wet string serial or parallel
interface - swap out the microcontroller, write some software to drive it and
have fun.
--
Phil. | (\_/) This is Bunny. Copy and paste Bunny
classiccmp at philpem.me.uk | (='.'=) into your signature to help him gain
http://www.philpem.me.uk/ | (")_(") world domination.