Motorola MVME172 - Manual (Page 200)

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MC2 Chip
3
General Control Register
FAST This control bit tailors the control circuit for BBRAM to
the speed of BBRAM.
When operating at 25 MHz, the FAST bit should be
cleared for devices with access times longer than 200 ns
(5 CLK cycles). The bit can be set for devices that have
access times of 200 ns or faster. It is not allowed to use
devices slower than 360 ns (9 CLK cycles), at 25 MHz.
When operating at 32 MHz, the FAST bit should be
cleared for devices with access times longer than 150 ns
(5 CLK cycles). The bit can be set for devices that have
access times of 150 ns or faster. It is not allowed to use
devices slower than 270 ns (9 CLK cycles), at 32 MHz.
MIEN Master Interrupt Enable. When this bit is high, interrupts
from and via the MC2 chip are allowed to reach the MPU.
When it is low, all interrupts from the MC2 chip are
disabled. Also, when the bit is low, all interrupt
acknowledge cycles to the MC2 chip are passed on, via
the IACKOUT* pin. This bit is cleared by a reset.
PPC PowerPC interrupt mode. When this bit is high, the
IPL<2> signal output is compatible with the int signal on
the PowerPC. When this bit is low, the IPL signal outputs
are compatible with the MC68060.
!
Caution
This bit is low for the MVME172 boards. Do not change it. If
it is changed, the board will not operate properly.
ADR/SIZ $FFF42000 (8 bits)
BIT 15 14 13 12 11 10 9 8
NAME SCCIT1 SCCIT0 PPC MIEN FAST
OPER R R R R/W R/W R/W R/W R/W
RESET 0 PL 0 PL 0 PL 0 PL 0 PL 0 PL 0 PL 0 P