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
429
On the BCM1250 Bits 104:0 of this register are selected in between TDI and TDO, on the BCM1125/H there
are two additional Broadcom Use Only bits so bits 106:0 are selected. The scan order is from LSB to MSB.
The configuration bits may be written by the JTAG probe while the part is held in reset using RESET_L
provided the cold reset delay (Tcr) described in the Hardware Data Sheet has elapsed since COLDRES_L was
released. Most of the other bits in this scanchain are for Broadcom Use Only, incorrect settings will cause the
part to behave in UNDEFINED ways and could require a full cold reset to restore deterministic behavior. The
CPU uniprocessor bits (in the resets field) are normally set by only on uniprocessor parts. However if one of
these bits is set in the control register and then the Broadcom-soft-reset bit is set, following the reset the
BCM1250 will behave as a uniprocessor. This can be used to disable one of the processors, it will not be
clocked and will enter a low power state.
Broadcom soft reset occurs only when a 1 is scanned into this register, and the TAP controller enters the
Update-DR state. This reset is just like a normal reset except that the contents of the system control register
are not reset. This allows testing of various modes.
TRACE Instruction
When the TRACE instruction is set, the trace_read register is selected between TDI and TDO. This is a read
only register. It is scanned out LSB first. The trace buffer should be frozen and the
startread
bit set prior to
reading out. This is a 64 bit register, and gets the next 64 bits of trace data every time the Capture-DR state is
entered. It performs just as if the data had been read out using address
00_1002_0a08
. Following a capture
the first scan of the register returns UNPREDICTABLE data and the next will return the first valid bits. After the
entire contents of the trace buffer have been read, it will return all zeros.
PERF Instruction
The PERF instruction selects the performance registers for scan in and out. Note that the value scanned in will
overwrite the counters. The performance chain is scanned out LSB first and is made up of the performance
registers as shown in
103:104
str_mode
2’b0
Broadcom Use Only, sets stretch mode for PLL. Set to zero for normal operation.
Table 302: System Control Scan Chain
(Cont.)
system_cfg -
00_1002_0008
Bits
Name
Default
Description
Table 303: Performance Counter Scan Chain
Bits
Register
Description
33:0
perf_cnt_cfg[33:0]
Performance counter configuration (See
).
74:34
perf_cnt_0[40:0]
Performance counters (See
115:75
perf_cnt_1[40:0]
156:116
perf_cnt_2[40:0]
197:157
perf_cnt_3[40:0]