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December 14, 2001
79RC64574 79RC64575
ferring data between the processor and memory at a peak rate of
1000MB/sec. A boot-time selectable option to run the system interface
as 32-bits wide—using basically the same protocols as the 64-bit
system—is also supported.
A
boot-time mode control interface
initializes fundamental
processor modes and is a serial interface that operates at a very low
frequency (SysClock divided by 256). This low-frequency operation
allows the initialization information to be kept in a low-cost EPROM;
alternatively, the twenty-or-so bits could be generated by the system
interface ASIC or a simple PAL. The boot-time serial stream is shown in
Table 3.
Serial
Bit
Description
Value & Mode Setting
0
Reserved
Must be set to 0.
1:4
Transmit-data-
pattern.
Bit 4 is MSB
64-bit bus width:
0: DDDD
1: DDxDDx
2: DDxxDDxx
3: DxDxDxDx
4: DDxxxDDxxx
5: DDxxxxDDxxxx
6: DxxDxxDxxDxx
7: DDxxxxxxDDxxxxxx
8: DxxxDxxxDxxxDxxx
9-15: Reserved. Must not be selected.
32-bit bus width:
0: WWWWWWWW
1: WWxWWxWWxWWx
2: WWxxWWxxWWxxWWxx
3: WxWxWxWxWxWxWxWx
4: WWxxxWWxxxWWxxxWWxxx
5: WWxxxxWWxxxxWWxxxxWWxxxx
6: WxxWxxWxxWxxWxxWxxWxxWxx
7: WWxxxxxxWWxxxxxxWWxxxxxxWWxxxxxx
8: WxxxWxxxWxxxWxxxWxxxWxxxWxxxWxxx
9-15: Reserved. Must not be selected.
5:7
PClock-to-
SysClk-Ratio.
Bit 7 is MSB
0: 2
1: 3
2: 4
3: 5
4: 6
5: 7
6: 8
7: Reserved
8
Endianness
0: Little endian
1: Big endian
9:10
Non-block write
Mode. Bit 10 is
MSB
00: R4400 compatible
01: Reserved
10: Pipelined-Write-Mode
11: Write-Reissue-Mode
Table 3 Boot-time Mode Stream (Page 1 of 2)
The
clocking interface
allows the CPU to be easily mated with
external reference clocks. The CPU input clock is the bus reference
clock and can be between 33 and 125MHz. An on-chip
phase-locked-
loop (PLL)
generates the pipeline clock (PClock) through multiplication
of the system interface clock by values of 2,3,4,5,6,7 or 8, as defined at
system reset. This allows the pipeline clock to be implemented at a
significantly higher frequency than the system interface clock. The
RC64574/575 support both single data (one byte through full CPU bus
width) and 8-word block transfers on the SysAD bus.
The RC64574/575 implement additional
write protocols
that
double the effective write bandwidth
. The write re-issue has a repeat
rate of 2 cycles per write. Pipelined writes have the same 2-cycle per
write repeat rate, but can issue an additional write after WrRdy* de-
asserts.
11
TimerIntEn
Timer interrupt settings:
0: Enable Timer Interrupt on Int(5)
1: Disable Timer Interrupt on Int(5)
12
System Interface
Bus Width.
Interface bus width control settings:
0: 64-bit system interface
1: 32-bit system interface
13:14
Drv_Out
Bit 14 is MSB
Slew rate control of the output drivers:
10: 100% strength (fastest)
11: 83% strength
00: 67% strength
01: 50% strength (slowest)
15:17
Write address to
write data delay.
From 0 to 7 SysClk cycles:
0: AD...
1: AxD...
2: AxxD...
3: AxxxD...
4: AxxxxD...
5: AxxxxxD...
6: AxxxxxxD...
7: AxxxxxxxD...
18
Reserved
User must select ‘0’
19
Extend
Multiplication
Repeat Rate.
Initial setting of the “Fast Multiply” bit.
0: Enable Fast Multiply
1: Do not Enable Fast Multiply
Note:
For pipeline speeds >250MHz, this bit must
be set to ‘1’.
20:24
Reserved
User must select ‘0’
25:26
System
configuration
identifier.
Software visible in processorConfig[21:20]
0: Config[21:20] = Mode Bit [25:26]
Must be set to 0.
27:256
Reserved
User must select ‘0’
Serial
Bit
Description
Value & Mode Setting
Table 3 Boot-time Mode Stream (Page 2 of 2)