Motorola MVME5100 Programmer's Reference Manual page 140

Hawk PCI Host Bridge & Multi-Processor Interrupt Controller
2
WLRT
2-78
WLRTx 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.
00 Match write threshold mode (i.e. PSATTx WXFT)
01
10
11
RLRTx 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.
RLRT
00 Match read threshold mode (i.e. PSATTx RXFT or RMFT)
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:
XPAD = 256 - Clk,
where Clk is the frequency of the CLK input in MHz. The following table
shows the scale factors for some common CLK frequencies.
Frequency
Write lock resolution threshold
Immediate
FIFO full
FIFO full
Read lock resolution threshold
Immediate
FIFO less than 1 cache line
FIFO less than 1 cache line
XPAD
100 $9C
83 $AD
66 $BE
50 $CE
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