ACT apricot - Page 165

SERIAL INTERFACE
initialisation. Changing these under software control are
described
in subsequent sections.
Once channel B is initialised with the keyboard
parameters and the base address for the interrupt vector
(OOH to Write Register 2), transfer of data between the
Keyboard and the processors can proceed. The format of the
command bytes supplied to the Write Registers of channel B
during
initialisation are detailed below. The address
locations
utilised by channel B are described in a previous
section,
under the heading ."Processor Interface".
D7 DO
11 I 0 I x I x 11 I 0 I x I 0 I Write Register 4
D7
Y Lparity Off.
~ 1.5 stop bits/Tx character
~----- x32 clock rate
DO
8 bits/Tx character
DTR (RS232C Baud rate select bit)
x = not applicable to mode and application, program to O.