Force Computers SYS68K/CPU-40, Руководство пользователя

Страница: 329 / 372

SECTION 9 APPLICATION COMMAND INTERFACE PROGRAMMING GUIDE
2-1
2. The Complete Description of All Commands Provided by The Application
Command Interface
The following subsections describe each command provided by the Application Command Interface in
detail and discuss the appropriate structure of the Command Control Buffers to issue the particular
command through the Application Interface, as well as the structure of the Command Control Buffer
"returned" through the interface to the application.
2.1 The OPEN Command
The OPEN command requests to establish a logical connection between the application and a
physical device; the appropriate Command Control Buffer is structured as presented below.
Whenever an OPEN command is issued through the Application Command Interface the underlying
software verifies whether it is necessary to initialize the specific physical device. If a physical device
can be owned by more than one application, like floppy disk controllers, or SCSI controllers, the certain
device is being initialized only on the receipt of the very first OPEN command. In contrast, a physical
device, which may be owned by only one single application, like a serial channel of a serial
communication controller, is initialized upon the receipt of every OPEN command.
typedef struct _ccb_open_command
{
unsigned long _access_control_flags;
long ( *ME_system_call ) ( );
CCB *ccb_link;
long last_command;
unsigned long _reserved[ 7 ];
long command;
unsigned long logical_device_number;
unsigned long inquiry_mode;
unsigned long response_mode;
unsigned long data_exchange_mode;
unsigned long response_mode_address;
unsigned long _remnant[ 47 ];
} CCB_OPEN_COMMAND;