IDT EJTAG System
EJTAG Test Access Port
79RC32438 User Reference Manual
20 - 63
November 4, 2002
Notes
Data Register (TAP Instruction DATA, ALL, or FASTDATA)
Compliance Level
: Required with EJTAG TAP feature.
The read/write Data register is used for opcode and data transfers during processor accesses. The
width of the Data register is 32 bits for 32-bit processors and 64 bits for 64-bit processor. The value read in
the Data register is valid only if a processor access for a write is pending, in which case the data register
holds the store value. The value written to the Data register is only used if a processor access for a pending
read is finished afterwards, in which case the data value written is the value for the fetch or load. This
behavior implies that the Data register is not a memory location where a previously written value can be
read afterwards. Figure 20.30 shows the format of the Data register and Table 20.45 describes the Data
register field.
Fields
Description
Read/
Write
Power-up
State
Compli-
ance
Name
Bits
EJTAGver
31:29
Version 2.6
R
Preset
Required
R4k/Rk3
28
Indicated Rk4 or Rk3 privileged environ-
ment:
0: R4k privileged environment
R
Preset
Required
DINTsup
24
Indicates support for DINT signal from
probe:
0:
DINT signal from the probe is not sup-
ported by this processor
1:
Probe can use DINT signal to make
debug interrupt on this processor
R
Preset
Required
ASIDsize
22:21
Indicates size of the ASID field:
0:
No ASID in implementation
R
Preset
Required
MIPS16
16
Indicates MIPS16 ASE support in the
processor:
0:
No MIPS16 support
R
Preset
Required
NoDMA
14
Indicates no EJTAG DMA support:
1:
No EJTAG DMA support
R
Preset
Required
MIPS32/64
0
Indicates 32-bit or 64-bit processor:
0:
32-bit processor
See the R4k/R3k bit for indication of privi-
leged environment.
R
Preset
Required
0
27:25, 23,
20:17, 15,
13:1
Ignored on writes; return zeros on reads.
R
Preset
Required
Table 20.44 Implementation Register Field Description
31
0
Data
Figure 20.30 Data Register Format