Serial Port Information

Technical Details

The serial port is DTE, just like a normal PC. The supplied lead is a null modem one.

The harness is identical to the internal port (but with only TX/RX/GND/power supply on DTR, pin 4) but a female as opposed to a male.

The port's speed defaults to 115200bps but can be run at lower speeds or as fast as 230400bps. Note that RTS/CTS (though connected to lines on the SA) isn't implemented at driver level.

Dropping to the Shell

To get into the shell you need to have the developer image installed on your empeg. These instructions are for beta6 and most likely won't work with beta5. You can get the image from the Empeg Upgrade site.

Once you've installed the image use a comm program to access your serial port (see chart below.) Parameters for the serial port are 115200,8,N,1 no handshaking. Plug in your empeg player (if not already done.) Wait until you get music to make sure the player is started. Now type q and then <ENTER>. The prompt should come up.

Note: replace * with appropriate device number for your system.

Maximum Serial Port Speed

230400 works for us - Mike used to run with a 230400bps serial card to minimise zmodem times :)

Bear in mind that standard PC serials do not run 230,400 - even though windows offers you the option. The standard 1.8432Mhz serial clock with a x1 divisor gives max 115,200bps: you need at least a 3.6864Mhz serial clock into your 16c[56789]50 to get 230400bps.

Running at 230K

A patch for various Unix and Windows systems to support chips that emulate a 16550 but can actually run at > 115K is here.

The Linux patch has moved. I've tested it on Linux 2.2 but unfortunately it doesn't recognise my chip. The Linux patch is here.

According to Rogier Wolff: you can replace the 1.8x MHz crystal with a 14.x MHz so that the 14MHz crystal frequency will be multiplied by 7.something to get the 100MHz system clock. And it will be divided by 8 to get the base-clock for the SMC chip which has the dual 16550s on many ISA buses.