User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 15: JTAG and Debug Page
439
EJTAG C
ONTROL
R
EGISTER
This is a 12 bit register to control the various operations of the debug support modules.This register is selected
by shifting in the CONTROL instruction. Bits in the EJTAG Control Register can be set/cleared by shifting in
data; status is read by shifting out this register. This EJTAG Control Register can only be accessed by the TAP
interface.
Table 310: EJTAG Control Register
Bit
Name
Description
Use
Reset
Value
0
DM0
Debug Mode 0. This bit indicates the value of the EDEN signal from CPU0.
When this bit is set, it indicates that CPU0 is signalling a debug event (see
SB-1 CPU User Manual). This bit is read only, and any writes to it are
ignored.
R
X
1
DM1
Debug Mode 1. This bit indicates the value of the EDEN signal from CPU1.
When this bit is set, it indicates that CPU1 is signalling a debug event (see
SB-1 CPU User Manual). This bit is read only, and any writes to it are
ignored.
On the BCM1125/H this bit is not used and reads are UNPREDICTABLE.
R
X
2
EJTAG Break0 Setting this bit to 1 causes the DINT pin to CPU0 to be set. This allows the
probe to signal a debug interrupt to CPU0. The bit must be cleared to remove
the interrupt.
R/W
0
3
EJTAG Break1 Setting this bit to 1 causes the DINT pin to CPU1 to be set. This allows the
probe to signal a debug interrupt to CPU1.The bit must be cleared to remove
the interrupt.
On the BCM1125/H this bit is not used.
R/W
0
4
PrTrap0
Probe Trap0. Setting this bit to 1 forces the DBBOOT signal to CPU0 to 1.
This allows the probe to force CPU0 into debug mode upon the next
deassertion of reset. This bit is set on the Update-IR state of the
EJTAGBOOT instruction. It is reset on the Update-IR state of the
NORMALBOOT instruction or by asserting the TRST_L pin or by a rising
edge of TCK when the TAP controller is in the Test-Logic-Reset state. This
bit can also be set or cleared by scanning a 1 or 0 into this bit.
R/W
0
5
PrTrap1
Probe Trap1. This bit performs the same way as PrTrap0, except it does so
for CPU1.
On the BCM1125/H this bit is not used.
R/W
0
6
ProbEn
Probe Enable. Setting this bit to 1 will indicate that EJTAG memory is
handled by the probe, so processor accesses are answered.
0: The probe does not handle EJTAG memory transactions. Accesses to the
EJTAG memory space always returns 0.
1: The probe does handle EJTAG memory transactions.
When this bit is set the MaSl bit is used to determine if the probe is acting as
bus master or slave. See discussion in
.
Note that setting the PrTrap bits without this bit set causes an invalid state.
The EJTAGBOOT instruction will set this bit to 1. The NORMALBOOT
instruction will clear this bit. This bit is also cleared by asserting TRST_L or
by a rising edge of TCK while in the Test-Logic-Reset State.
R/W
0
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