Turbo232 Programming
Revision T v1.0.0



This document outlines the differences between SwiftLink and the 
Turbo232 cartridges. It assumes that the programming has knowledge of or 
separate information concerning programming SwiftLink.



GENERAL
The Tubro232 cartridge is functionally compatible with the operation of 
the original SwiftLink models designed by Dr. Evil Labs. However, the 
new version shares only the 6551 ACIA in common with the original 
designs, and has been completely redesigned to meet the goals of 
extending the capabilities of this product while maintaining functional 
compatibility.
   Three new speeds have been added (57.6Kbps, 115.2Kbps and 230.4Kbps) 
via an additional register which controls a programmable clock. In 
addition, the external IRQ/NMI switch has been discontinued, though this 
functionality is still available via an internal jumper block, which 
also allows for changes to the DSR configuration and default I/O 
address.
   Finally, the effect of 'mirroring' of registers throughout the I/O 
page has been reduced to 32 bytes, so that the product can be used 
without interference with GEORAM and similar devices. CMD can also 
provide custom programmed versions of the decoding chip used in the new 
product to change the base address to any 32-byte boundry within the 
selected I/O page; this latter provision is targeted at programmers who 
wish to create applications which use multiple Turbo232 cartridges 
within the same I/O page, as well as to users of such applications if 
and when they exist.



DETAILS
It is first important to note the different memory 'footprint' of the 
Turbo232. While SwiftLink contained only 4 registers whose contents were 
mirrored at every 4 memory locations throughout the I/O page occupied by 
the device, Turbo232 maps 8 register locations which are mirrored for 
only for 32 bytes from the base address. Of the four new register 
locations, only one is actually implemented: the ES (Enhanced Speed) 
register, located at an offset of $07 from the base address.
   For baud rates up to and including 38.4Kbps, Turbo232 is programmed 
just like a SwiftLink. The only possible cause for incompatibility that 
may be noted is the difference in mirroring of registers which might be 
used by some programs to detect the presence of a SwiftLink. It is this 
very difference, however, that will allow the programmer to determine 
whether a SwiftLink or a Turbo232 is installed (see "DETECTION 
ROUTINE").





   To obtain the new high-speed baud rates, you must first set the 
lowest four bits of the register located at offset $03 to zero (the 
upper 4 bits are insignificant). [Note: Setting these bits to zero will 
result in a value of 1 in the mode bit (bit 2) of the ES register.] You 
may then set the specific high-speed baud rate using bits 0 and 1 of the 
ES register. Since bit 2 of the ES register (mode bit) is read-only, and 
bits 3 through 7 are insignificant, you can safely program the rate by 
storing in that location a value of $00 for 230.4Kbps, $01 for 
115.2Kbps, or $02 for 57.6Kbps. [Note: Storing a value of $03 to the DS 
register isn't recommended, though it isn't harmful; it provides no 
clock output, but remains reserved for future expansion.]


REGISTER INFO


  $Dx00    DATA REGISTER       Same as original SwiftLink
  $Dx01    STATUS REGISTER     Same as original SwiftLink
  $Dx02    COMMAND REGISTER    Same as original SwiftLink
  $Dx03    CONTROL REGISTER    Same as original SwiftLink, plus
                               xxxx0000 sets enhanced-speed mode
  $Dx04    UNDEFINED
  $Dx05    UNDEFINED
  $Dx06    UNDEFINED


  $Dx07    ES REGISTER         7  6  5  4  3  2  1  0
                               x  x  x  x  x  M S1 S0
 
                                  M (bit 2) Mode (read-only)
                                    0 = Normal SL mode
                                    1 = Enhanced Speed mode


                                  S1, S0 (bit 1 and bit 0) Speed
                                  (read-only if M=0)
                                    00 = 230,400 bps
                                    01 = 115,200 bps
                                    10 =  57,600 bps
                                    11 = undefined, no clock output
                                         reserved for future expansion


DETECTION ROUTINE
The following can be used to determine if an installed SwiftLink is the 
standard or Enhanced Speed type:


  LDA #$00
  STA $Dx03
  LDA $Dx07


After executing this code, the A register will contain a zero if a 
standard SwiftLink is installed, but will be non-zero if a Turbo232 is 
installed. 