MVME5100 Single Board Computer Programmer's Reference Guide

2
Hawk PCI Host Bridge & Multi-Processor Interrupt Controller
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.
WLRT Write lock resolution threshold
00 Match write threshold mode (i.e. PSATTx WXFT)
01 Immediate
10 FIFO full
11 FIFO full
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 Read lock resolution threshold
00 Match read threshold mode (i.e. PSATTx RXFT or RMFT)
01 Immediate
10 FIFO less than 1 cache line
11 FIFO less than 1 cache line
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 XPAD
100 $9C
83 $AD
66 $BE
50 $CE
2-78 Computer Group Literature Center Web Site