Specifications

7.2 COMMAND LOOP
The host ma~ reauest the VS100 to perform WGA commands at
this point. The followin~ commands are defined at microcode level:
1. Reset (~o to Idle Loop via Powerup diasnostics)
2. Send_Command_Packet (includes Move_Object and Report_Status Commands)
3. Start_Displa~_Firmware (transfers control to the displa~ firmware)
4. Init (initialise CSR's and ~o to command loop)
Init initialises the Control/Status Re~isters as follows:
1 • CSR
to (Control/Status ReSister)
Untouched; taboo!
2.
CSR
+1
(Interrupt
Reason
Resister)
Bit
1
(--
Init_Done
3. CSR
+2
(Peripheral
Event
Re~ister)
Cleared
4. CSR
t3
(Function Parameter
Low) Unibus_Ram base
address
low
5. CSR
+4
(Function Parameter
Hish)
Unibus_Ram
base
address
hish
7. CSR
t5
(Identification
Resister) Bits 3-5
(--
hardware
ID
6.
CSR
t6
(Unused Resister)
Cleared
8.
CSR
t7
(Interrupt
Vector
Resister)
Untouched; taboo!
CSR's +5/6 are the X and Y Mouse/Tablet Cursor Position Re~isters once the
displa~ firmware has been downloaded. Refer to the Workstation Graphics
Architecture document for details on the Control/Status Re~isters.
After the first command, we wait in a loop for five
seconds for another command. If we do not receive another command in
that time, we assume the host is dead in the water, put UP the Link
Down icon, and exit the command loop to re-enter Idle Loop.