HP Vectra Technical Reference Manual page 104

4.3 Hardware Interface Level
The hardware interface of the Input System is composed of a set of drivers to respond to
hardware interrupts and process physical data from the input devices into a form usable by
the application interface drivers. These drivers are shown in Figure 4.2.
4.3.1 Overview
This section describes the drivers, data structures, and interrupt service routine (ISR) event
processing that takes place below the application interface level. The following data flow
expands on step 2 of the data flow presented in Section 4.2.1. A detailed explanation of each
step is presented after the data flow.
1. The user touches the screen. This causes a hardware interrupt which is managed by the
8259A interrupt controller service (V_S8259). V_S8259 responds to the interrupt
controller chip and transfers control to the HP-HIL driver.
2. The HP-HIL driver (V_HPHIL) services the HP-HIL controller chip, retrieving the input device
data. V_HPHIL processes the input data and transfers control to the Input System dispatch
service.
3. The dispatch service (V_SINPUn transfers control to the appropriate physical device driver
based on the source of the input data (in this case the physical touch screen driver).
4. The physical touch screen driver builds the Physical Describe Record and transfers control to
the application interface driver V_LTOUCH.
V_S8259 provides a funnel point for managing HP specific hardware. The Input System
hardware communicates with the hardware interface drivers via three interrupts: the 8041
service request (SVC), the 8041 Output Buffer Full (OBF), and the HP-HIL controller interrupt. The
8041 SVC and OBF interrupts are discussed in the keyboard section (Section 5). The HP-HIL
controller interrupt is chained to the HP-HIL driver (V_HPHIL), i.e., when V_S8259 receives an
HP-HIL controller interrupt it generates an HP_ENTRY software interrupt to transfer control to
V_HPHIL.
The HP-HIL driver services the HP-HIL controller and generates the appropriate Physical ISR Event
Record(s). After processing the input data V_HPHIL chains to V_SINPUT.
Input System and HP-HIL 95