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April 10, 2001
IDT79RC4650
The following is a list of the supported external requests:
◆
Read Response
◆
Null
Boot-Time Options
Fundamental operational modes for the processor are initialized by
the boot-time mode control interface. The boot-time mode control inter-
face is a serial interface operating at a very low frequency (MasterClock
divided by 256). The 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.
To initialize all fundamental, operational modes, immediately after the
VCCOK signal is asserted, the processor reads a serial bit stream of 256
bits. After initialization is complete, the processor continues to drive the
serial clock output, but no further initialization bits are read.
Boot-Time Modes
The boot-time serial mode stream is defined in
Table 5. Bit 0 is the bit
presented to the processor when VCCOK is asserted; bit 255 is the last.
Power Management
CP0 is also used to control the power management for the RC4650.
This is the standby mode and it can be used to reduce the power
consumption of the internal core of the CPU. The standby mode is
entered by executing the WAIT instruction with the SysAD bus idle and
is exited by any interrupt.
Standby Mode Operation
The RC4650 provides a means to reduce the amount of power
consumed by the internal core when the CPU would otherwise not be
performing any useful operations. This is known as “Standby Mode.”
Entering Standby Mode
Executing the WAIT instruction enables interrupts and enters
Standby mode. When the WAIT instruction finishes the W pipe-stage, if
the SysAd bus is currently idle, the internal clocks will shut down, thus
freezing the pipeline. The PLL, internal timer, and some of the input pins
(Int[5:0]*, NMI*, ExtReq*, Reset*, and ColdReset*) will continue to run. If
the conditions are not correct when the WAIT instruction finishes the W
pipe-stage (i.e. the SysAd bus is not idle), the WAIT is treated as a NOP.
Once the CPU is in Standby Mode, any interrupt, including the inter-
nally generated timer interrupt, will cause the CPU to exit Standby
Mode.
Thermal Considerations
The RC4650 utilizes special packaging techniques to improve the
thermal properties of high-speed processors. The RC4650 is packaged
using cavity down packaging in a 208-pin QFP (DP). The QFP package
allows for an efficient thermal transfer between the die and the case.
The R4650 and the RV4650 are guaranteed in a case temperature
range of 0
°C to +85°C for commercial temperature parts and in a case
temperature range of -40
°C to +85°C for industrial temperature parts.
The type of package, speed (power) of the device, and airflow conditions
affect the equivalent ambient temperature conditions that will meet this
specification. The equivalent allowable ambient temperature, TA, can be
Mode bit
Description
255..15
Must be zero
14..13
Output driver strength:
10
→ 100% strength (fastest)
11
→ 83% strength
00
→ 67% strength
01
→ 50% strength (slowest)
11
Disable the timer interrupt on Int[5]
12
0
→ 64-bit system interface
1
→ 32-bit system interface
10..9
00
→ RC4000 compatible
01
→ reserved
10
→ pipelined writes
11
→ write re-issue
80
→ Little endian
1
→ Big endian
7..5
Clock multiplier:
0
→ 2
1
→ 3
2
→ 4
3
→ 5
4
→ 6
5
→ 7
6
→ 8
7 reserved
4..1
Writeback data rate:
64-bit
0
→
1
→ DDx
2
→ DDxx
3
→ DxDx
4
→ DDxxx
5
→ DDxxxx
6
→ DxxDxx
7
→ DDxxxxxx
8
→ DxxxDxxx
9-15 reserved
32-bit
0
→
1
→ WWx
2
→ WWxx
3
→ WxWx
4
→ WWxxx
5
→ WWxxxx
6
→ WxxWxx
7
→ WWxxxxxx
8
→ WxxxWxxx
9-15 reserved
0
Reserved (must be zero)
Table 5 Boot-time mode stream