Download module

This software module

1) Controls the shift register that drives the download LEDs

2) Senses the presence of the 3.5’ floppy drive

3) Keeps track of the progress of the hypothetical download used in the game

Public Functions:

initDownload

Initialize internal download state

If disk is already in

Can’t start download until disk is ejected and reinserted

Update all timer variables with current time

Make sure all progress bar LEDs are off

resetDownload

Call initDownload

isDiskIn

Return disk status with debouncing

clearDownloadDisplay

Clear out shift register with all zeros

checkDownloadEvents

Read disk status with debouncing software

State machine using internal state

Case Initial_State

If disk is in

If not waiting on disk eject

Start download progress

Update LEDs

Change state to Running

Else

Blink LEDs

Return NO_EVENT

Else

Blink LEDs

Return NO_EVENT

Case RUNNING

If disk is in

Update progress bar LEDs

If download is complete

Change state to completed

Return DOWNLOAD_COMPLETE_EVENT

Else

Change state to stopped

Return DOWNLOAD_STOPPED_EVENT

Case STOPPED

If disk is in

Change state to running

Return DOWNLOAD_STARTED_EVENT

Case COMPLETED

Blink LEDs

Return DOWNLOAD_COMPLETE_EVENT

For all states, if nothing was returned, return DOWNLOAD_NO_EVENT

blinkDownloadLEDs

If enough time has passed blink the LEDs

If LEDs are currently on

Fill shift register with all zeros

Else

Fill shift register will all ones

Module Functions:

checkDiskStatus

If enough time has passed (based on the cal for debouncing the switch)

Read disk switch input

advanceDisplay

Load a 1 into the shift register (turns on the next LED)

pulseShift

Set the shift register clock line to HI

Kill some time

Set the shift register clock line to LO