Specifications

EPC-8 Hardware Reference
F F
F-10
Reserved (814C & 814D)
These registers are reserved and return 1s when read. Writes to these registers have no
effect.
Message Low Register (814E & 814F)
RAM Lower
RAM Upper
There are actually two 16 bit registers at this address , outgoing and incoming 16 bit
registers (UART model). A write from the PC side fills the outgoing register. This
register can only be read from the VME port and when this occurs the RRDY bit is
deasserted in the Response register. A read from the PC side reads the incoming
register. The incoming register can only be written to from the VME bus port and
when this occurs, the WRDY bit is deasserted in the Response register.
VME A31-24 Address Register (8150)
VMEbus A31-24 Address register (WA31-24)
This register is one of several that supply the VMEbus address bits when the EPC-8
makes an access in its "E page." This register supplies VME address bits A31-A24.
VME Modifier Register (8151)
VME WA23-22 BORD IACK AM5 AM4 AM2 AM1
This register is also used when the EPC-8 makes an access through its E page to the
VMEbus. Bits 7 and 6 provide VME address bits A23 and A22, respectively. Bits 3-
0 define the value placed on the associated VMEbus address-modifier lines. Register
bits are not defined for the VMEbus address-modifier AM3 and AM0 lines since, for
all defined address-modifier values in the VMEbus specification, AM3 is 1 and AM0
is the inverse of AM1. Therefore these two bit values are generated by hardware.
Note that because AM3 and AM0 are hardware generated, the EPC-8 does not support
user-defined address-modifiers.
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