Reference Manual

PMAC 2 Software Reference
PMAC Saved Setup Registers 389
VME/DPRAM Addressing Setup Registers: X:$0783 – X:$078C
There are ten saved setup registers that configure the VME bus interface, including DPRAM. In ISA-bus
PMACs, two of these registers configure the optional DPRAM interface.
X:$0783 VME Address Modifier
Range: $00 - $FF
Units: None
Default: $39
X:$0783 controls which address modifier value PMAC will respond to when sent by the VME bus host.
X:$0783 takes one of three valid values in normal use, depending on the address bus width used:
• X:$0783 = $29: 16-bit addressing
• X:$0783 = $39: 24-bit addressing
• X:$0783 = $09: 32-bit addressing
X:$0783 is actually used at power-on/reset only, so to set or change the VME address modifier, change
the value of X:$0783, store this new value to non-volatile flash memory with the SAVE command, and
reset the card with the $$$ command. The active register into which the value of X:$0783 is copied at
power-on/reset is X:$E006 bits 0 – 7. It is permissible to write to this register directly (suggested M-
variable M90) to change the active setup without a SAVE and reset.
X:$0784 VME Address Modifier Don’t Care Bits
Range: $00 - $FF
Units: None
Default: $04
X:$0784 controls which bits of the X:$0783 VME address modifier are don’t care bits. X:$0784 is set to
$04 in all normal use, which permits both “non-privileged” and “supervisory” data access by the VME
host.
X:$0784 is actually used at power-on/reset only, so to set or change the VME address modifier “don’t
care” bits, change the value of X:$0784, store this new value to non-volatile flash memory with the SAVE
command, and reset the card with the $$$ command. The active register into which the value of
X:$0784 is copied at power-on/reset is X:$E007 bits 0 – 7. It is permissible to write to this register
directly (suggested M-variable M91) to change the active setup without a SAVE and reset.
X:$0785 VME Base Address Bits A31-A24
Range: $00 - $FF
Units: None
Default: $FF
X:$0785 controls bits A31 through A24 of the VME bus base address of PMAC, both for the mailbox
registers, and the dual-ported RAM. It is only used if 32-bit addressing has been selected with X:$0783
and X:$078C.
X:$0785 is actually used at power-on/reset only, so to set or change bits 16-23 of the VME bus base
address, change the value of X:$0785, store this new value to non-volatile flash memory with the SAVE
command, and reset the card with the $$$ command. The active register into which the value of
X:$0785 is copied at power-on/reset is X:$E008 bits 0 – 7. It is permissible to write to this register
directly (suggested M-variable M92) to change the active setup without a SAVE and reset.