VME VMIVME-2131, Instruction Manual

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3.5 REGISTER CONTROL LOGIC
The register control logic for the VMIVME-2131 Board is designed to
support write and read operations to and from the eight 8-bit bi-directional dual-port
latches and write transfers to a CSR that controls the test mode and front panel
LED. The control logic provides the capability to read or write 8, 16, or 32 bits of
data. This control logic is implemented in PALs as shown on the schematic in
Appendix A.
3.6 CONTROL AND STATUS REGISTER (CSR)
The CSR is a write-only register that controls the Test Mode (TM) bit and
the front panel Fail LED as shown in Figure 3.6-1. The TM bit disables the output
drivers to perform Built-in-Test functions. Both bits of the CSR are initialized active
upon system reset or power-up such that the driver outputs are disabled and the
front panel LED is illuminated. A jumper H1 is configured such that when writing a
logic "one" to bits 6 and 7 of the CSR, the LED is illuminated and the output drivers
are off-line.
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