Motorola MVME5100 Programmer's Reference Manual page 116

WLRTx
WLRT
00
01
10
11
RLRTx
RLRT
00
01
10
11
The PPC Prescaler Adjust Register (XPAD) is used to specify a scale
factor for the prescaler to ensure that the time base for the bus timer is
1MHz. The scale factor is calculated as follows:
where Clk is the frequency of the CLK input in MHz. The following table
shows the scale factors for some common CLK frequencies.
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Write Lock Resolution Threshold. This field is used by
the PHB to determine a PPC bound write FIFO threshold
at which a bridge lock resolution will create a retry on a
pending PCI bound transaction. The encoding of this field
is shown in the following table.
Write lock resolution threshold
Match write threshold mode (i.e. PSATTx WXFT)
Immediate
Read Lock Resolution Threshold. This field is used by
the PHB to determine a PPC bound read FIFO threshold
at which a bridge lock resolution will create a retry on a
pending PCI bound transaction. The encoding of this field
is shown in the following table.
Read lock resolution threshold
Match read threshold mode (i.e. PSATTx RXFT or RMFT)
Immediate
FIFO less than 1 cache line
FIFO less than 1 cache line
XPAD = 256 - Clk,
Frequency XPAD
100
83
66
50
FIFO full
FIFO full
$9C
$AD
$BE
$CE
Registers
2
2-77