Texas Instruments TMS320C3 Series, User Manual, Page: 136 / 166

Communications Kernel Source Code
A-8
;********************************************************************;
; KERNEL COMMANDS ;
; ––––––––––––––– ;
; These commands are the primary functions required by the kernel ;
; to perform host based communications. They have been packed into ;
; the avalable memory in such a way as to minimize the kernels size. ;
; The non–debugger functions have also been placed after the debugger;
; commands making it easier to simply allow the application to ;
; ’overwrite’ the debugger commands. ;
;********************************************************************;
;====================================================================;
; INTx is the starting point for all host generated commands. ;
; A host generated command is received when INT2 goes active (driven ;
; low) indicating HPSTB has gone low and that the host would like to ;
; transfer a piece of data or command. ;
;====================================================================;
INTx ; maxspeed
push ST ; Push ISR variables
push DP ;
push R0 ; NOTE: A HALT command pops these
push IR1 ; values followed by a full save
push AR0 ;
push AR1 ;
ldp @JUMP ; Get address of command from JUMP table
ldi @S0_xdata,R0 ; Put a zero in the DXR making startup
sti R0,@S0xdata ; from a stalled port safe for the AIC
ldi 0,R0 ; which cannot accept ’garbage’ which
sti R0,@S0_xdata ; would reprogram it.
tstb 4,IF ; Get here by driving INT2 low
bz SR2 ; Make sure INT2 is active
call R_HOST ; R0==command
ldi R0,AR1 ;
addi @JUMP,AR1 ;
ldi *AR1,AR1 ;
b AR1 ; execute command
;********************************************************************
; COMN is used by both the XWRIT and XREAD functions to receive the
; block transfer length, address and address increment value.
;********************************************************************
COMN call R_HOST ;
ldi R0,AR1 ; data packet length
call R_HOST ;
ldi R0,AR0 ; source address
call R_HOST ;
ldi R0,IR1 ; source index
subi 1,AR1 ;
rets ;