24 May
2010
24 May
'10
12:52 p.m.
On 5/24/10, Chuck Guzis <cclist at sydex.com> wrote:
On 24 May 2010 at 9:46, Ethan Dicks wrote:
Neat.
That sounds cool. I have a few examples of 5380
implementations
(uVAX2K, Amiga, ISA, 68K Mac...)...
The 53C400 datasheet was an eye-opener. When I grabbed a Trantor
T130 card, I was surprised to find that it was a very wierd bird
indeed. The 53C400 can decode all 20 bits of an 8-bit ISA address,
provides for 8 address ranges, as well as handshake for DMA and IRQ
and EPROM chip select. Basically, to do an 8 bit ISA controller, you
need only an LS245, a 2764 EPROM (if you want to boot with it) and
the 53C400. Access is all memory-mapped I/O. The T130 takes this and turns it on its head with two
PALs, making
the 53C400 I/O port mapped (at least partially). It's a needlessly
convoluted design. I wonder if the intention was to emulate an older
5380 design.
It's likely. I have a T128 that came with my original NEC CDR-72
drive from DAK (that happens to have a boot ROM, so I have a bootable
8-bit SCSI interface for 8-bit PCs!) I can imagine that the T-130 was
made to superficially resemble the T-128, at least from either a
driver or boot ROM architecture standpoint (especially the memory
mapped vs I/O mapped part).
-ethan