Artesyn MVME5100, Programmer'S Reference Manual, Page: 136 / 318

Hawk PCI Host Bridge & Multi-Processor Interrupt Controller
MVME5100 Single Board Computer Programmer’s Reference (6806800H17B )
136
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:
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:
Table 2-36 Read Lock Resolution Threshold
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
Table 2-37 Common Scale Factors for Common CLK Frequencies
Frequency XPAD
100 $9C
83 $AD
66 $BE
50 $CE