The VIC Interface

The use of the VICbus in the VCC 2117 offers a link between a CAMAC system and a controlling computer system on distances up to 100 meters.
The VICbus interface provides a transparent access to the local CPU bus and to the CAMAC functions. For data exchange between the CPU and other computer systems via the VICbus, a Dual Port SRAM has been implemented.
From the VICbus side, a 16 Mbytes addressing area is accessible in the VCC 2117.
The VICbus Interface features:

Compatibility with the VIC 8250 and VIC 8251
32-bit slave interface on the VICbus (supports also 8- and 16-bit accesses)
Slave only capability
Support for block transfer (256 LWords maximum when starting at a 1 Kbyte address boundary)
Release On Register Access (RORA) Interrupter
VICbus interrupter. The Vertical Interrupt number corresponds to the VICbus device number.

The resource accessed depends on the type of VIC cycle decoded by the VCC 2117:

Direct Compelled cycles access the VIC Control and Status Registers (VIC CSR)
Transparent VME cycles are decoded to access the resources of the CPU bus: EPROM, Z-CIOs, Ethernet, Private SRAM, Dual Port SRAM, ... (VCC 2117B only)
Transparent VME cycles with an AM code of $10 access the CAMAC dataway directly when the VCC is not equipped with its processor (VCC 2117A).

The CAMAC dataway can be accessed in two different ways from the VICbus side:

Either through the List Processor (VCC 2117B only). In this case, the remote VIC master device writes in the Dual Port SRAM a list of N, F and A commands to be executed in the CAMAC Crate. The VCC's CPU then treats each one of those commands, reporting the results in the Dual Port SRAM, which is finally read back in block mode by the remote VIC master,
Or directly through the Dual Port SRAM (VCC 2117A and VCC 2117B). Every CAMAC command (a special encoding of N, F and A) is allocated a specific Dual Port SRAM memory location. Writing or reading to a certain memory location generates the corresponding CAMAC command. This is a slow way of accessing CAMAC, which is not recommended for On-Line Data Acquisition but offers sufficient performance for Control applications.