Data Sheet
March 2000
DSP1627 Digital Signal Processor
Lucent Technologies Inc.
123
12 Timing Characteristics for 2.7 V Operation
(continued)
12.2 Reset Circuit
The DSP1627 has a powerup reset circuit that automatically clears the JTAG controller upon powerup. If the supply
voltage falls below V
DD
MIN* and a reset is required, the JTAG controller must be reset—even if the JTAG port isn’t
being used—by applying six low-to-high clock edges on TCK with TMS held high, followed by the usual RSTB and
CKI reset sequence. Figure 60 shows two separate events: an initial powerup and a powerup following a drop in the
power supply voltage.
*
See Table 60, Recommended Operating Condiitons.
Notes:
See Table 62 for CKI electrical requirements and Table 151 for TCK timing requirements.
When both INT0 and RSTB are asserted, all output and bidirectional pins (except TDO, which 3-states by JTAG control) are put in a 3-state
condition. With RSTB asserted and INT0 not asserted, EROM, ERAMHI, ERAMLO, IO, DSEL, and RWN outputs remain high, and CKO remains
a free-running clock.
TMS and TDI signals have internal pull-up devices.
Figure 60. Powerup Reset and Chip Reset Timing Diagram
* With external components as specified in Table 62.
T
TCK
= t12 = TCK period. See Table 151 for TCK timing requirements.
Table 148. Timing Requirements for Powerup Reset and Chip Reset
Abbreviated Reference
t8
t9
t146
Parameter
Min
6T
—
2T
20
20
Max
—
10
—
—
—
—
—
—
—
—
—
Unit
ns
ms
ns
ms
μ
s
ns
ns
Reset Pulse (low to high)
V
DD
Ramp
V
DD
MIN to RSTB Low CMOS
Crystal*
Small-signal
t151
t152
TMS High
JTAG Reset to
RSTB Low
6 * T
TCK
2T
CMOS
Crystal*
Small-Signal
20 ms – 6 * T
TCK
if 6 * T
TCK
< 20 ms
0 if 6 * T
TCK
≥
20 ms
20 μs – 6 * T
TCK
if 6 * T
TCK
< 20 μs
0 if 6 * T
TCK
≥
20 μs
—
t153
RSTB (low to high)
54
ns
5-2253 (F).a
t10
t11
t10
t11
t9
t146
t8
t9
t151
t152
t8
V
DD
RAMP
CKI
TCK
TMS
RSTB
PINSV
OH
V
OL
V
IH
V
IL
V
IH
0.4 V
V
DD
MIN
V
DD
MIN
0.4 V
t153
t153