Technical information

CHAPTER 4
Expansion Features
Expansion Bay 67
User Installation of an Expansion Bay Module 4
The user can insert a module into the expansion bay while the computer is
operating. This section describes the sequence of control events in the computer
and gives guidelines for designing an expansion bay module so that such
insertion does not cause damage to the module or the computer.
IMPORTANT
The user must not remove a module from the expansion
bay while the computer is communicating with the module
or, for a module with a disk drive, while the disk is
spinning. ▲
Sequence of Control Signals 4
Specific signals to the Paddington IC allow the computer to detect the insertion
of a module into the expansion bay and take appropriate action. The sequence
of events is diagrammed in Figure 4-3.
When a module is inserted, the computer performs the following sequence of
events:
1. When a module is inserted, the /DEV_IN signal goes low, causing the
Paddington IC to generate an interrupt.
2. System software responds to the interrupt and reads the DEV_ID pins to
determine the type of module inserted.
3. System software sets the /MB_PWR_EN signal low, which turns on the
power to the expansion bay.
4. System software sets the enable signal and internally notifies the appropriate
driver of the presence of a newly inserted module.
5. System software sets the /MB_RESET signal high to bring the expansion bay
module out of reset.
Essentially the reverse sequence occurs when a module is removed from the
expansion bay:
6. When the module is removed, the /DEV_IN signal goes high. The
Paddington IC responds by setting /MB_PWR high, the enable signal low,
and /MB_RESET low, and generating an interrupt. System software
responds to the interrupt and notifies the appropriate driver that the module
has been removed.