HONEYWELL 51454363-175模块，51454363-175产品外观
磁盘输入/输出支持187Bug可以通过与通信启动磁盘输入/输出VMEbus上的智能磁盘控制器模块。本节包括：❏ 区块与扇区❏ 设备探针功能
❏ 通过187Bug命令进行磁盘输入/输出
❏ 通过187Bug系统调用进行磁盘输入/输出
❏ 默认控制器和设备参数
❏ 磁盘输入/输出错误代码磁盘支持设施
187Bug中内置的磁盘支持设施包括：❏ 命令级磁盘操作
HONEYWELL 51454363-175模块❏ 磁盘输入/输出系统调用（仅通过其中一个陷阱#496说明）供用户程序使用
❏ 磁盘参数的定义数据结构参数表参数，例如映射模块的地址和连接到控制器模块的设备的类型和数量由187Bug保存在表格中。这些参数的默认值在通电和冷启动重置时分配，但可以根据需要进行更改在本章后面关于默认参数的部分中进行了描述。
支持的控制器附录B包含当前支持的控制器列表，如以及每个控制器的默认配置列表。区块与扇区逻辑块定义了磁盘设备的信息单元。A.187Bug将磁盘视为划分为逻辑磁盘的存储区域阻碍。默认情况下，逻辑块大小设置为256字节
阻止系统中的设备。块大小可以在每个基于IOT命令的设备。
该部门将媒体本身的信息单元定义为：由控制器查看。扇区大小因不同而异控制器和特定设备的值可以显示和使用IOT命令更改。当请求磁盘传输时，传输的开始和大小以块为单位指定。187Bug将其转换为等效值扇区规范，然后将其传递给控制器启动传输。如果从块到扇区的转换产生如果是分数扇区计数，则返回一个错误，并且不返回任何数据转移。
Disk I/O Support
187Bug can initiate disk input/output by communicating with
intelligent disk controller modules over the VMEbus.
This section covers:
❏ Blocks Versus Sectors
❏ Device Probe Function
❏ Disk I/O via 187Bug Commands
❏ Disk I/O via 187Bug System Calls
❏ Default 187Bug Controller and Device Parameters
❏ Disk I/O Error Codes
Disk Support Facilities
Disk support facilities built into 187Bug consist of the following:
❏ Command-level disk operations
❏ Disk I/O system calls (only via one of the TRAP #496
instructions) for use by user programs
❏ Defined data structures for disk parameters
Parameter Tables
Parameters such as the address where the module is mapped and
the type and number of devices attached to the controller module
are kept in tables by 187Bug. Default values for these parameters
are assigned at powerup and cold-start reset, but may be altered as
described in the section on default parameters, later in this chapter.
Supported Controllers
Appendix B contains a list of the controllers presently supported, as
well as a list of the default configurations for each controller. Blocks Versus Sectors
The logical block defines the unit of information for disk devices. A
disk is viewed by 187Bug as a storage area divided into logical
blocks. By default, the logical block size is set to 256 bytes for every
block device in the system. The block size can be changed on a per
device basis with the IOT command.
The sector defines the unit of information for the media itself, as
viewed by the controller. The sector size varies for different
controllers, and the value for a specific device can be displayed and
changed with the IOT command.
When a disk transfer is requested, the start and size of the transfer
is specified in blocks. 187Bug translates this into an equivalent
sector specification, which is then passed on to the controller to
initiate the transfer. If the conversion from blocks to sectors yields
a fractional sector count, an error is returned and no data is
transferred.
