non-CP/M Z80 board - test-drb@ccmp.vtda.org

19 Jun 2008

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Subject: Re: non-CP/M Z80 board
   From: ard at p850ug1.demon.co.uk (Tony Duell)
   Date: Thu, 19 Jun 2008 04:42:01 +0100 (BST)
     To: cctalk at classiccmp.org

   I think
the chips under discussion were the 8085 specialty chips,
 8155, 8355, 8755, etc.  Got tubes of those?  
    I've got a dozen or so 8755s, two or three 8155s, and no 8355s.   
 Not tube quantities, unfortunately. 
IIRC the 8355 was the mask-progeammed part, so it's not suprising you 
don't have any of those, If you did, they proably wouldn't contain the 
code you wanted :-).  
Yes, but it' still useful as an IO device with 16 IO port lines that could 
individually set for input or output.

...
 The 8755 was the EPROM part, and at least one 
version had a quartz windo for erasure (I don't know if there was an OTP 
type). The 8155 was RAM. All had I/O as well. 
There was never an OTP, all were windowed Eprom devices.  

the 8155 and the '56 were the same device save for CS polarity.  they
are very useful with 256bytes ram, a programable timer/baud rate generator
and 22 IO pins that can be set as output, input or strobned outpus and inputs.

...
 There's also the 8156, which is the same as the
8155 (RAM + I/O) but with 
an active-high chip select. Not as common as the 8155. 
Not as widely used but I have a bunch.

...
 Of course you can use normal RAM and EPROM with the
8085 is you add and 
address latch. An 74x373, or the 74x573 which as a saner pinout, is a 
common choice.

There was also the 8185 wich was a 1Kx8 ram with muxed address/data.  
Those were uncommon as intel was the only supplier.

The 8085A (or A-5), 8755, 8155 in three chips gave 256bytes ram,
2Kbytes Eprom, 38 configurable port lines, A timer/baudrate generator,
4 interrupt lines and the handy SID and SOD IO pins.  Very handy 
for small applications.  The base part ran at 3mhz (3.072mhz) and 
the faster A-5 was a 5mhz (there were 6mhz HmosII and CMOS parts 
later).

Substitute a 8088 (or V20) and 8284A for the 8085 and you had a 16it 
cpu with all the Eprom, ram and IO listed.

Allison

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 -tony 