12.6.2 LAN ESCC

Der LAN Port / ESCC

Pinout for the LAN-Port / Modem adaptor cable

Urgent:
On the Mini-DIN plug you have to connect Pin 4 AND Pin 8 to GND. The only way for the symetric input of the LAN-Port for a defined signal.

The hole connection works with hardware handshake in both directions if you use the HSMODAxx-SCC driver. HSModem drivers switch RTS/CTS handshake transparent to a DTR/CTS handshake an allows a higher bit transfer.

Ask you local electronic dealer for the right mini DIN8 plug. Ready to use cables are not avaiable, so you have to make your own cable. Mac serial cables doasn't work, they are all have a different pin out.

Modify LAN-Port

Question:

I want to hook up my Mega STe, TT and Falcon via the LAN ports. I will be using STing, and IP masquerading.
 

Answer:

The `LAN ports' are just regular serial ports only with different electrical characteristics, they're not faster or anything like that... (at least electritcally its the same thing macs used for their early slow way of networking called `appletalk', but to use them like that you'd need special drivers which may still not exist.)
 

Handling:

Anyway i'd just use null modem cables, connect the `normal' serial ports (which go to the same uart chip) and set up 115200 bps slip links with header compression. (or ppp, but slip has less overhead and for fixed links ppp's features are of no use.)

 
Actually I believe the TT and Falcon ports can do 230400 too but i'm not sure about the other machines... and use modem2 and/or serial2, modem1 is on a different uart that can only do 19200 bps. Make the fastest machine the router (and NAT box, i.e. the TT), meaning you'll have one slip link from the TT to the Mega STe and one from the TT to the Falcon. Actually since these are all ataris you could also use plip (parallel port ip) for one of the links, thats a bit faster than serial...

 
And btw 115200 bps slip is also what i used years ago to link my Mega STe to the unix (BSD) box and it had no problems getting some 10K/sec throughput with ftp. (well ok, that was with a hardware fix, see below...) It even for a while did uucp-i over tcp to my `ISP' over that link after i switched from analog to isdn (with the BSD box routing the packets to isdn, single channel sync raw-ip) and that little 68000 then exchanged my mail and news with nearly isdn speed (sending and receiving at the same time) and still had CPU cycles free.

 

The hardware fix:

On the Mega STe atari screwed up (at least on mine, but others reported similar problems): With the original SCC chip (thats the uart that controls the faster serial ports) serial IO on those ports could interfere with disk DMA(!), which had me searching for a long time for mysterious data corruption even though the protocol on the serial link discovered _no_ CRC errors. (anyone who still knows what protocol i was porting back then gets a virtual cookie!)

 
When i finally replaced the SCC with a better pin-compatible Zilog one the problem went away... this chip was also mentioned in the hsmodem docs, i didn't change its clock tho. It also has 8 bytes FIFO on each channel, the original one only had 3, so if you get `silo overflows' at the higher speeds (receiver overrun, would cause tcp/ip to have to resend packets) that would be a way to fix those too. Actually as i remember on the TT the SCC also had DMA channels but i have never heared of them actually being used... (that would be another way to get rid of receiver overruns, and it would lower the CPU load too. But of course receiver overruns are more likely to occur on the machines with the slower CPUs, where you don't have the luxury of DMA on the SCC.)
 
If you replaced the original 85C30 in your MegaSTE, TT or Falcon by an AM85C230A or Z85230, you can use ESCC.PRG instead of SCC.PRG. In the state of delivery these computers contain only a SCC, then use the SCC.PRG. If you modified your falcon by drawing out the MODEM1 interface not existent in the original state, you can use additionally MFP_FALC.PRG for this interface.

 
Who installed the hardware ST_ESCC in his computer, uses additionally ST_ESCC.PRG. Who has other interface modifications, should read the textes and may ask me, if he finds nothing.
 

SCC, ESCC an ST_ESCC Driver

These all are drivers for the serial interfaces realized by a SCC or ESCC (eg IC Z8530, Am85C30, Z85230). They work together with DRVIN.PRG.

Falcon SCC only can be modified with Z8530, Am85C30 or an Z85230 chip. Other won't work!

These ICs all hade an 8 byte receiver FIFO and a transmitter FIFO with 4 byte. An ESCC contains -all- functions of an normal Falcon SCC. After installtion of one of the ESCCs have have to use HSModem7 package from Harun Scheutzow.

On the Falcon, if equipped with a speeder with FastRAM) *SCC*.PRG must be loaded into physical RAM, they should _not_ be loaded into virtual RAM!

The drivers detect automatically whether there is a PCLK clock frequency of 8MHz or 14745600Hz and display it rate in their installation message.

Some technical Data taken from HSModem7 Doku, Harun Scheutzow