
Rev. B
|
Page 18 of 44
|
May 2005
ADSP-21266
Power-Up Sequencing
The timing requirements for DSP startup are given in
Table 10
and
Figure 6
.
Table 10. Power-Up Sequencing (DSP Startup)
Parameter
Min
Max
Unit
Timing Requirements
t
RSTVDD
t
IVDDEVDD
t
CLKVDD
t
CLKRST
t
PLLRST
RESET Low Before V
DDINT
/V
DDEXT
On
V
DDINT
On Before V
DDEXT
CLKIN Valid After V
DDINT
/V
DDEXT
Valid
1
CLKIN Valid Before RESET Deasserted
0
ns
–50
200
ms
0
10
2
20
3
200
ms
μs
PLL Control Setup Before RESET Deasserted
μs
Switching Characteristic
t
CORERST
DSP Core Reset Deasserted After RESET Deasserted
4096t
CK
4,
5
1
Valid V
/V
assumes that the supplies are fully ramped to their 1.2 and 3.3 volt rails. Voltage ramp rates can vary from microseconds to hundreds of milliseconds
depending on the design of the power supply subsystem.
2
Assumes a stable CLKIN signal, after meeting worst-case startup timing of crystal oscillators. Refer to the crystal oscillator manufacturer’s data sheet for startup time.
Assume a 25 ms maximum oscillator startup time if using the XTAL pin and internal oscillator circuit in conjunction with an external crystal.
3
Based on CLKIN cycles.
4
Applies after the power-up sequence is complete. Subsequent resets require a minimum of four CLKIN cycles for RESET to be held low in order to properly initialize and
propagate default states at all I/O pins.
5
The 4096 cycle count depends on t
SRST
specification in
Table 12
. If setup time is not met, one additional CLKIN cycle may be added to the core reset time, resulting in
4097 cycles maximum.
Figure 6. Power-Up Sequencing
CLKIN
RESET
t
RSTVDD
RSTOUT
VDDEXT
VDDINT
t
PLLRST
t
CLKRST
t
CLKVDD
t
IVDDEVDD
CLK_CFG1–0
t
CORERST
MULTIPLEXEDWITHCLKOUT
*
*