Page 14
Front Panel Operation
In its default configuration, the 8800c Front Panel board set duplicates the operation of the original Al-
tair front panel. In addition, the following features can be selectively enabled as desired:
• Power-on to a valid reset state
• An output latch at I/O address 0FFh that can display on the data LEDs
• Auto repeat single-step at selectable rate from 1hz-8hz, similar to the 8800b
• Code snippet injection: Common Altair bootstrap loaders, port echo routines, Kill-the-Bit, etc.
can be injected into RAM by selecting the desired code snippet on the lower eight address
switches, then depressing the AUX-Left switch.
• Auto jump on power-on (can be independent of reset operation)
• Auto jump on reset (can be independent of power-on operation)
These features are configured using three 8-bit “virtual” DIP switches (VDIPs). The following paragraphs
define the VDIP settings for each option. The process of setting the value of the virtual DIP switches is
covered in the “Updating Virtual DIP Switches” section further down in this manual.
7
6
5
4
3
2
1
0
VDIP #1
Pwr Reset
FF Latch
Code Inj
----
----
Auto-Steps/sec (zero disables)
VDIP #2
MSB of Power-On Jump Address (zero disables)
VDIP #3
MSB of Reset Jump Address (zero disables)
Power-On Reset
By default, and to behave like the original Altair 8800 front panel, the run state of the 8800c Front Panel
is indeterminate at power-on and the 8080 is not given a RESET. This, in turn, tends to leave the 8080
processor in an invalid state as well. This is the reason for the manual STOP/RESET that must be per-
formed on the Altair front panel after power on.
To get around this problem, the 8800c Front Panel can be configured to automatically perform a
STOP/RESET during power-up. To enable this feature, set bit 7 of VDIP #1 to 1. To disable automatic re-
set, set the bit to 0.
Output Latch at 0FFh
An output latch can be enabled at I/O address 0FFh. The latch content can be displayed on the eight da-
ta LEDs on the front panel. The AUX-Right switch is used to choose between displaying the output latch
or normal output on the data LEDs.
While the computer is running, pressing the AUX-Right switch down displays the output latch on the da-
ta LEDs. Conversely, raising the AUX-Right switch restores normal display on the data LEDs.
Behavior while the computer is stopped is slightly different. When stopped, the normal LED display is
important for virtually every operation performed. Therefore normal data is automatically shown when-
