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Register Descriptions
3.1.25
External Timer Registers
The MVME4100 provides a set of tick timer registers for access to the four external timers
implemented in the timers/registers PLD. Note that these registers are 32-bit registers and
are not byte writable. The following sections describe the external timer prescaler and
control registers.
3.1.25.1 Prescaler Register
The Prescaler Adjust value is determined by this formula:
Prescaler Adjust=256-(CLKIN/CLKOUT)
Where CLKIN is the input clock source in MHz and CLKOUT is the desired output clock
reference in MHz.
Table 3-28
REG
BIT
Field
OPER
RESET
The prescaler provides the clock required by each of the four timers. The tick timers require
a 1 MHz clock input. The input clock to the prescaler is 25 MHz. The default value is set for
$E7 which gives a 1 MHz reference clock for a 25 MHz input clock source.
44
Prescaler Register
Prescaler Register - 0xF202 0000 (8 bits of a 32-bit register)
7
6
Prescaler Adjust
R/W
$E7
MVME4100 Single Board Computer Programmer's Reference (6806800H19D)
5
4
3
Register Descriptions
2
1
0
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