Motorola MVME172 - Manual (Page 226)

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MC2 Chip
3
Tick Timer 4 Compare Register
Tick Timer 4 Counter
Bus Clock Register
The Bus Clock Register should be programmed with the hexadecimal
value of the operating clock frequency in MHz (i.e., $21 for 33 MHz). The
MC2 chip uses the value programmed in this register to control the refresh
timer so that the DRAMs are refreshed every 15.6 microseconds. After
power-up, this register is initialized to $10 (for 16 MHz).
ADR/SIZ $FFF42038 (32 bits)
BIT 31 . . . 0
NAME Tick Timer 4 Compare Register
OPER R/W
RESET 0 P
ADR/SIZ $FFF4203C (32 bits)
BIT 31 . . . 0
NAME Tick Timer 4 Counter
OPER R/W
RESET X
ADR/SIZ $FFF42040 (8 bits)
BIT 31 30 29 28 27 26 25 24
NAME BCK5 BCK4 BCK3 BCK2 BCK1 BCK0
OPER R/W R/W R/W
RESET 0 P 0 P 0 P 1 P 0 P 0 P 0 P 0 P