Re: TI-H: TI-85 RAM
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Re: TI-H: TI-85 RAM
>From: "Paul Kraszewski" <PKraszewski@BigFoot.com>
>To: "TI Hardware" <ti-hardware@lists.ticalc.org>
>Subject: TI-H: TI-85 RAM
>Date: Wed, 29 Jul 1998 13:38:31 +0200
>Reply-To: ti-hardware@lists.ticalc.org
>
>
>Hi everybody!
>
> I've recently signed some TI lists (ones having anything to do
>with TI85). I hope none of them is dead... Well - here's my question:
>TI85 has 128kb ROM, right? How the hell it is possible with address
>lines A0-A15???? I am sure, that 16 address lines with 8-bit o
>rganization gives 64kb. Not a bit more. How's that? CPU seems to have
>16 address lines, too.
The CPU is a custom Z80 chip made by Toshiba. It has a Z80 core w/ some
internal logic. One of these internal logic circiuts is a paged memory
logic circuit. It takes in an 3 bit code for the ROM(port 7) and it
outputs the correct signals that select the ROM page.(I think it does
this only when accessing a page area) The ROM is the lower 32K of the
address space. The lowest 16K is Page 0, which is always available.
The next 16K of address space is the paged ROM section. It has 7
possible pages.
>
> I know it uses banking, but at least ROM should have 17 address
>lines to have 128kb. Or perhaps the banking is done by ROM i
>nternally??? I haven't heard of such a memory, but nobody knows...
The paged mem logic puts the 3bit page data on the address bus
indepented of the CPU, Selectes the ROM and executes a read.
>
> Regarding the last discussion about sockets, I've installed in my
TI85 an extra socket, under the ENTER key. It is a 10pin IDC sock (one
ripped form PC COM port on MB - I do plenty of things from elements
ripped from old PC equipment), with connects to power and link. The
power is connected via diode switch (gee, I need Shottky low drop
diodes;), so connecting external power supply won't blow batteries and
external devices can't be run off internal batteries. Now I have
integrated power/serial cable. And the socket (black silhouette) looks
nearly as an original equipment. Thie only drawback is the spaghetti
inside - it is really hard to close the cover due to cables inside ;(
>
> More to linking topics (hopefully, electrical side is all the same)
- did anyone think about using I2C repeaters (Philips' P82B715) do
extend link range? Philips claims they built 400m I2C connection using
two P82B715 and a flat ribbon cable (every second wire grounded). Using
some extra stuff (current pumps) they built a 1 mile (1828.8m) I2C
connection. Seems impressive to me. See Philips' WWW page AN452 (1 mile
conn.) and AN444 (400m connection) for details.
>
> You may use link to direct-connect TI calculators to I2C
microcontrollers (eg. 80552, some PICs). If you hack CBL/CBR protocol,
you may do lots of interesting stuff, including sophisticated data
aquisition hardware.
>
> The last, but not the least - you may easily make solid state
diskette (SSD) using:
> a. 87C552 - master control
> b. as much CMOS SRAM (battery backed up) as necessary,
> c. few keys and LCD display to select program to be sent back
to TI
>
> d. optional - perhaps 1.44" disk drive????
>
> The system could work as active receiver - it listens to TI all
>the time. If TI sends data, it is immediately stored in SSD RAM. If
>user wants to retrieve program, selects it on LCD display and sets TI
>to hearing - it is loaded right back. Note - this is a 'legal'
>solution, I mean it needs no shells, managers or drivers.
This would be cool, but it would better to use the EII. This idea would
be time-consuming, and expensive. But still feasable, if you want to do
it, go ahead
>
> Keep developing,
> Best regards,
> Pawel Kraszewski - mailto:pkraszewski@BigFoot.COM
> /\ http://www.bigfoot.com/~pkraszewski
>__/ \ ______________________Tel/Fax: +48(91)4872905______________
> \/
>
>P.S. Is there *ANY* TI85 link program working fine (I mean fast) on NT?
>
>
>
Matt Butch
mjb25@hotmail.com
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