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IDT EJTAG System
Functional Description
79RC32438 User Reference Manual
20 - 5
November 4, 2002
Notes
Memory-mapped EJTAG Memory
The memory-mapped EJTAG memory is located in the debug memory segment (dmseg), which is a
subsegment of the debug segment (dseg). It is accessible by the debug software when the processor is
executing in Debug Mode. The EJTAG probe handles all accesses to this segment through the Test Access
Port (TAP), whereby the processor has access to dedicated debug memory even if no debug memory was
originally located in the system. General information about the debug segment and memory is found in
section “Debug Mode Address Space” on page 20-7.
EJTAG Test Access Port Registers
The probe accesses EJTAG Test Access Port (TAP) registers (shown in Table 20.5) through the TAP, so
the processor can not access these registers. These registers allow specific control of the target processor
through the TAP. General information about the TAP registers is found in section “TAP Data Registers” on
page 20-59.
Data Breakpoint
ASID n
DBASIDn
ASID value to compare for breakpoint
n.
See section “Data Break-
point ASID n (DBASIDn)
Register” on page 20-49.
Data Breakpoint
Control n
DBCn
Control of breakpoint n match on load/
store, data bytes, access to data bytes,
comparison of ASID, and generated
event on match.
See section “Data Break-
point Control n (DBCn) Reg-
ister” on page 20-49.
Data Breakpoint
Value n
DBVn
Data value to match for breakpoint n.
See section “Data Break-
point Value n (DBVn) Regis-
ter” on page 20-51.
Register
Name
Register
Mnemonic
Functional Description
Reference
Device ID
none
Identifies device and accessed processor in
the device.
See section “Device Identifi-
cation (ID) Register (TAP
Instruction IDCODE)” on
page 20-61.
Implementation
none
Identifies main debug features implemented
and accessible through the TAP.
See section “Implementa-
tion Register (TAP Instruc-
tion IMPCODE)” on page
20-62.
Data
none
Data register for processor accesses used
to support the EJTAG memory.
See section “Data Register
(TAP Instruction DATA,
ALL, or FASTDATA)” on
page 20-63.
Table 20.5 Overview of Test Access Port Registers (Part 1 of 2)
Register
Name
Register
Mnemonic
Functional Description
Reference
Table 20.4 Overview of Data Hardware Breakpoint Registers (Part 2 of 2)