
Data Sheet
March 2000
DSP1629 Digital Signal Processor
Lucent Technologies Inc.
101
11 Timing Characteristics for 2.7 V Operation
(continued)
11.2 Reset Circuit
The DSP1629 has two external reset pins: RSTB and TRST. At initial powerup, or if the supply voltage falls below
V
DD
MIN* and a device reset is required, both TRST and RSTB must be asserted to initialize the device. Figure 37
shows two separate events:
I
Chip reset at initial powerup.
I
Chip reset following a drop in power supply.
Note:
The TRST pin must be asserted even if the JTAG controller is not used by the application.
*
See Table 60, Recommended Operating Conditions.
*
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, and RWN outputs remain high, and CKO remains a
free-running clock.
See Table 62 for input clock electrical requirements.
Figure 37. Powerup Reset and Chip Reset Timing Diagram
Note:
The device needs to be clocked for at least six CKI cycles during reset after powerup. Otherwise, high cur-
rents may flow.
Table 108. Timing Requirements for Powerup Reset and Chip Reset
Abbreviated Reference
t8
t9
t146
Parameter
Min
6T
—
2T
Max
—
10
—
—
54
Unit
ns
ms
ns
μs
ns
RSTB and TRST Reset Pulse (low to high)
V
DD
Ramp
V
DD
MIN to RSTB Low
CMOS
Small-signal
t153
RSTB (low to high)
—
Table 109. Timing Characteristics for Powerup Reset and Chip Reset
Abbreviated Reference
t10
t11
Parameter
Min
—
—
Max
100
100
Unit
ns
ns
RSTB Disable Time (low to 3-state)
RSTB Enable Time (high to valid)
V
DD
RAMP
RSTB,
TRST
OUTPUT
PINS*
CKI
t11
V
OH
V
OL
V
IH
V
IL
t9
t146
t10
0.4 V
V
DD
MIN
t11
V
DD
MIN
0.4 V
t10
t9
t146
t153
t8
t153
t8
5-4010 (F).a