Figure: A TCPIP-VME Interface (A2064F). The A2064F uses the RCM3200 TCPIP module (red plug-in circuit) to transfer image data 360 KBytes/s to a LWDAQ client.
| Schematic | PCB | Assembly |
The A2064 resides in standard VME crates and implements a LWDAQ Relay. Together with VME-resident LWDAQ Drivers such as the A2037A, the A2064 acts as a LWDAQ Server.
The A2064 always acts as a VME master. It translates commands it receives in LWDAQ TCPIP Messages into VME backplane read and write operations that control VME-resident LWDAQ Drivers. The A2064 is a VME 6U card with two 96-pin DIN plugs on the back side. It can select slaves with either 24-bit or 32-bit addresses.
The following table gives the existing versions of the A2064.
| Version | Description |
|---|---|
| A2064X | A206401B PCB, RCM2200 relay, socket at board center, 160 kBytes/s. |
| A2064A | A206401C PCB, RCM2210 relay, socket at board edge, 160 kBytes/s |
| A2064F | A206401C PCB, RCM3200 relay, socket at board edge, 360 kBytes/s |
The A2064's LWDAQ Relay is an RCM2200, RCM2210, or RCM3200. The relay communicates with a VME Interface via a 6-bit control address and an 8-bit data bus. The heart of the VME Interface is a programmable logic chip. You will find the logic programs for all versions of the A2064 here. The programs are in the ABLE language. The P2064A code is for the A2064X and A2064A.
VME-resident LWDAQ Drivers each have a base address, which is the location of the first byte they occupy in the VME address space. The LWDAQ Driver with VME Interface (A2037A), for example, provides thirteen switches that set the top thirteen bits of its 32-bit base address. The VME Interface on the A2064 contains four eight-bit registers that specify the 32-bit base address of the VME Driver with which it will communicate. These base address registers reside in control address space, as specified in the following table.
| Base Address Register | Address Location |
| DBA3 (most significant byte) | 42 |
| DBA2 | 43 |
| DBA1 | 44 |
| DBA0 (least significant byte) | 45 |
The A2064's VME Interface overlaps the controller address space of the driver with which it communicates. Whenver the A2064's LWDAQ Relay writes to the control addresses 42 to 45, these writes are directed to the A2064's VME Interface, and set the base address registers. When the base address is zero, the LWDAQ Relay reads and writes from locations in the VME Interface's address space. Because the control address is only six bits long, only 64 registers are available in the VME Interface. When the base address is non-zero, the VME Interface adds the control address to the base address to create the VME address it will use for a read or write cycle over the VME backplane. When the A2064 adds the base address and the control address, it assumes that the bottom 6 bits of the base address are zero. It uses the 6 control address bits to generate the lower 6 bits of the VME address.
The A2064 performs only eight-bit data reads and writes. Communication over the VME backplane would be faster with sixteen or thirty-two bit reads and writes, but the A2064's performance is limited by its TCPIP connection, not by the VME backplane. Even with single-byte reads, the backplane provides 2 MByte/s. The TCPIP data rate, meanwhile, is only 360 kBytes/s in the A2064F and 160 kBytes/s in the A2064X and A2064A.
All instrument panels in the LWDAQ Software allow the user to set the A2064 base address with a hexadecimal string by means of the daq_driver_socket parameter. To select driver socket 1 on the driver with base address $00E00000, set daq_driver_socket to "00E00000:1".
Note: All our schematics and Gerber files are distributed under the GNU General Public License.
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