58457



     SIO (below) to control the actual peripheral(s). CIO treats all I/O
     in the same manner: device independent. The differentiation
     between operations is done by the actual device drivers.

     You jump to here to use the IOCB handler routines in ROM.
     BASIC supports only record I/O or one-byte-at-a-time I/O (GET
     and PUT). Addressing CIOV directly will allow the user to input
     or output a buffer of characters at a time, such as loading a
     machine language program directly into memory from a disk file.
     This is considerably faster than using BASIC functions such as
     GET. Here is a typical machine language subroutine to do this:

     PLA, PLA, PLA, TAX, JMP $E456
     (104,104,104,170,76,86,228)
     ($68,$68,$68,$AA,$4C,$56,$E4)

     This gets the IOCB number into the 6502 X register and the
     return address on the stack. CIOV expects to find the IOCB
     number 16 in the 6502 X register (i.e., IOCB zero is zero, IOCB
     one is 16; $10, IOCB two is 32, $20, etc.). $E456 is the CIO
     initialization entry point (this address).

     To use CIOV in a program, first you must have OPENed a
     channel for the appropriate actions, POKEd the correct IOCB
     (locations 848 to 959; $350 to $3BF) with the correct values, and
     established a location in which to load your file (IOCB address
     plus four and plus five). One use is calling up a high-res picture
     from a disk and storing it in the screen memory (locations 88, 89;
     $58, $59). You can POKE the appropriate decimal values into
     memory and call it with a USR call, or make it into a string
     (START$ = "hhh*LVd" where the * and the d are both inverse
     characters) and call it by:

     JUMP = USR(ADR(START$))

     This method is used to start the concurrent mode in the RS-232 of
     the 850 interface in the 850 Interface Manual. See location 88, 89
     ($58, $59) for another example of the machine language routine
     technique. Still another use of this method can be found in De Re
     Atari. Initialized to 58564 ($E4C4).

58457          E459           SIOV
     Serial Input/Output (SIO) utility entry point. SIO drives the
     serial bus and the peripherals. When a request is placed in the
     Device Control Block (DCB) by a device handler, SIO takes
     control and uses the data in the DCB to perform the operation
     required. SIO takes care of the transfer of data as defined by the
     DCB. CIO (above) is responsible for the "packaging" of the data
     and transfers control to SIO when necessary. See the DCB
     locations 768 to 779 ($300-$30B).