Files for the AWA RT85A - Royal District Nursing Service versions.
Mark Harrison, VK3BYY, Feb 2002

WARNING: This patch should only be applied to the RDNS RT85A with
the Hitachi HD6305 microprocessor and 2764 8kbyte EPROM.

FILE CONTENTS:
==============
This zip file contains files to modify the RT85A that uses the 2764 EPROM,
and makes the follow functions work correctly:

 - Scan function to work above channel 39,
 - Low power select from link on back of control head (Depower link).
 - Low power on selected channels.
 - Disable Emergency SELCALL button in software

PERSONALITY DATA:
=================
BITS.txt is a list of personality (option) bits that apply to this and the 2716 EPROM version of the RDNS RT85A radios.

The Scan and Power link options require bits to be set in the personality data.

PROBLEMS WITH ORIGINAL EPROM:
=============================
The original EPROM in the RDNS radios have been modified from the original RT85
to support a SELCALL emergency button (the big red button on the front of the
control head), and to relay a transmission from a portable alarm transmitter
carried by the nurses.
Once the button is pressed, the radio continues to transmit a SELCALL message
every 10 seconds until either the radio receives an aknowldge SELCALL from the base station, or the PTT is pressed.
This can be REALLY annoying if someone accidentally bumps the button when the radio
is on your local repeater!
 
It appears that the emergency feature cannot be disabled in the personality bytes.
The modifications made to implement this feature appear to have corrupted the scanning and the Hi/Lo power link options.

PATCH TO FIX RDNS BUGS:
=======================
PATCH8K0.A05 is a file contains the source code for a patch to fix the bugs.
PATCH8K0.S19 is the Motorola S19 format file for overlaying the original EPROM data.

To use the S19 file:
 - start your EPROM programmer software,
 - read in the EPROM (or appropiate file image).
 - read in the PATCH8K0.S19 file
   (file is type: MOTOROLA)
   (address = 0000)
   ( choose unused bits = "don't care")
   ( - do NOT let it set unused bytes to 0 or $FF else it wipes out the EPROM image data)
 - blow the EPROM and/or save the block $0000-$1FFF to a file for next time.

POWER ADJUSTMENT:
=================

The follwing adjustments need to be made before the low power option will work:
(Note: By feault, RDNS radios seem to run in low power mode, but have the power adjusted for maximum output! - ).

Set the Depower option in the personality byte (bit 7 or address $13F1) to select output power with the links on the back of the control head.
Alternatively, change the first byte of channel data from $FF to $00 for each channel that will operate in low power mode, and do not set the Depower option.

Rotate both trim pots in the PA section to fully clockwise (RV501 & RV502).
With a dummy load and power meter, remove the depower link from the head (or select a high power channel), and adjust RV502 to the required high power output level.

Insert link (or select low power channel) and adjust RV501 for desired low power setting.
Power levels may change as the PA warms up so repeat adjustments after transmitting for a few minutes.

PATCH SOURCE:
=============

The patch source code (PATCH8K0.A05) is provided for anyone that cares to
experiment further.
I used the 6805 AS5 assembler - it's available from most good DOS freeware sites.

Good Luck,
Mark, VK3BYY