viii Changing the Value of an Argument 0 , , " 0 0 0 0 , , , , 122 Utility: Put-value ... , . 0 , , , , , , , , , , , 122 Utility: Put-element, ... , ... , , , , , , , , 123 Utility: Put-bytes ........ , . , ..... , . , .. , , 124 Utility: Put-elem-bytes .... , ...... , , ................................. " , 125 Using Common ........ , ,', ,.,.", , ,." 127 Busy bits ............ , ... , ... " ..... ,., ........ ,. o. ,'" 130 Utility: Busy. , . . . . . . . . . . .. . ..... , , ......... , , , , , , , 131 Chapter 7: I/O Handling Peripheral-Processor Communication. , , ..... , .. 0 133 Interfaces ....... , ........ , , ............ , ... , . , .......................... , .
, 134 Registers ., .. " .. , ......... , ....... ', ....... , ........... " .. , ... ,' ......... 134 Status and Control Registers ....... , ....... , .......................... " .... 136 Status and Flag Lines, .... , , .. , ... , " ..... , ......... , .. , .... , ........... , .... 137 Select Codes ....... , , , , , , ,' , , , 134 Programmed I/O ...... , , .... " .' ... , .. , ..... , ........................ , ... , .. , 138 Interrupt I/O ... , , .. , , ,." , " , , , , " 138 Priorities .. , ......... , , , 140 Interrupt Service Routines and Linkage ... , , , , , ,., 140 Access .... , .. , . , ' , , ,. , , , , 141 Utility: Isr-access . , .. , ........ , .......... , .... , . , ......
, ............... 143 State Preservation and Restoration ............. , ... , ......... 0 ,. . . , . 145 Indirect Addressing in ISRs , .................... , .................... , .... , ., 146 Direct Memory Access (DMA) ., .... , .... , .. , .. , 147 DMA Registers ,.... . ............... ' ................... , ....... " ........ 148 DMA Transfers. , .... , , ...... , ...................... , . . . . .. . ............... 149 BASIC Branching on Interrupts .... " ..... " ........... , .... , .. , .. " ... , ........ 150 Signalling, .. " .... , ...... , ..... , , , , , , , , , ,. 151 Additional Pre-Defined Symbols, 0 , , , , 153 ON INT Statement .. , ........................ , . , .....
, 150 Prioritizing ON INT Branches ........ , , .. , , , , 153 Environmental Considerations ..... , , .... , ....... , .... , ...... , ............... 155 Disabling ON INT Branching ., ....... , .............. ' ............ , ... , ...... 156 Mass Storage Activities . , ...................... , ........................ , ....... 156 Reading from Mass Storage ., .......... , ............... , ..... , ... ,. , 157 Utility: Mm-read-start ...... , " ..• , 158 Utility: Mm-read-xfer .. , ............ , ......... , .... , ......... ,., ..... 159