Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Writing a Host Communications Program
391
Initializing the Interrupt Controller
To start, write to the Turbo PMAC PIC’s Initialization Command Words (ICWs) to set up the PIC
properly. Although this IC is on Turbo PMAC, it is mapped into the PC’s port space as two registers at
Turbo PMAC’s base address plus 8 and 9.
properly. Although this IC is on Turbo PMAC, it is mapped into the PC’s port space as two registers at
Turbo PMAC’s base address plus 8 and 9.
To do this, perform the following steps:
1. Write a byte of 17(hex) to [PMAC base address + 8]. This sets up ICW1 for edge-triggered
interrupts.
2. Write a byte of 08(hex) to [PMAC base address + 9]. This sets up ICW2.
3. Write a byte of 03(hex) to [PMAC base address + 9]. This sets up ICW4 for 8086-mode operation.
4. Write a byte of FF(hex) to [PMAC base address + 9]. This writes to Operation Control Word 1 to
3. Write a byte of 03(hex) to [PMAC base address + 9]. This sets up ICW4 for 8086-mode operation.
4. Write a byte of FF(hex) to [PMAC base address + 9]. This writes to Operation Control Word 1 to
mask all eight interrupts into the Turbo PMAC PIC.
Unmasking Interrupts
When you are ready to accept interrupts from PMAC, unmask the interrupt(s) into the PMAC PIC that
you want active. You write a one-byte argument to {PMAC base address + 9] in which every masked
interrupt to the Turbo PMAC PIC is represented by a 1; and every unmasked interrupt is represented by a
0. For instance, to unmask IR4 alone, the argument would be EF(hex); to unmask IR5 alone, the
argument would be DF(hex).
When you are ready to accept interrupts from PMAC, unmask the interrupt(s) into the PMAC PIC that
you want active. You write a one-byte argument to {PMAC base address + 9] in which every masked
interrupt to the Turbo PMAC PIC is represented by a 1; and every unmasked interrupt is represented by a
0. For instance, to unmask IR4 alone, the argument would be EF(hex); to unmask IR5 alone, the
argument would be DF(hex).
At this point, unmask the interrupt being used on the PC’s PIC. First, disable the PC interrupts (TurboC
command: disable(); ). Next, read the current mask word at I/O port address 21(hex) with a command
such as:
command: disable(); ). Next, read the current mask word at I/O port address 21(hex) with a command
such as:
ch = inportb(0x21)
Then unmask the new interrupt that will be used by performing a bit-by-bit AND between the current
mask word and a mask word that would enable only the new interrupt line -- EF(hex) for IRQ4, F8(hex)
for IRQ3. The C command for this is:
mask word and a mask word that would enable only the new interrupt line -- EF(hex) for IRQ4, F8(hex)
for IRQ3. The C command for this is:
ch = ch & 0xef
The resulting new mask word is written back to I/O port address 21(hex) with:
outportb (0x21, ch)
Finally, re-enable the PC interrupts (TurboC command: enable();). This completes the setup procedure.
Using the Interrupts
To react to an interrupt in actual use, write an interrupt service routine. Exactly how this is done depends
on the operating system and the programming language. Consult the documentation for these items for
further details.
on the operating system and the programming language. Consult the documentation for these items for
further details.
PCOMM32 Library Support
Delta Tau’s PCOMM32 and PCOMM32PRO programming libraries for Microsoft Windows operating
systems support ISA and PCI interrupts and handle the setup automatically through its routines. Consult
the documentation for these libraries for details.
systems support ISA and PCI interrupts and handle the setup automatically through its routines. Consult
the documentation for these libraries for details.
VME Bus Communications
A VME-bus Turbo PMAC communicates over the VME bus as a slave device through a set of sixteen 8-
bit “mailbox registers,” each of which can hold one character and can be accessed from both the bus and
the Turbo PMAC processor. Optionally, there is also a dual-ported RAM IC with 8192 shared 16-bit
registers that can be used for either ASCII-text communications or transfer of binary values.
bit “mailbox registers,” each of which can hold one character and can be accessed from both the bus and
the Turbo PMAC processor. Optionally, there is also a dual-ported RAM IC with 8192 shared 16-bit
registers that can be used for either ASCII-text communications or transfer of binary values.