ADSP-2126x SHARC Processor Hardware Reference
15-13
System Design
If the
TRST
pin is not asserted (or held low) at power-up, the JTAG port is
in an undefined state that may cause the processor to drive out on I/O
pins that would normally be three-stated at reset. The
TRST
pin can be
held low with a jumper to ground on the target board connector.
A detailed discussion of JTAG and its use can be found in the Engi-
neer-to-Engineer Note (EE-68),
Analog Devices JTAG Emulation Technical
Reference
. This document is available on the Analog Devices Web site at
www.analog.com.
Phase-Locked Loop Startup
The
RESET
signal can be held low long enough to guarantee a stable
CLKIN
source and stable
VDDINT
/
VDDEXT
power supplies before the PLL is reset.
In order for the PLL to lock to the
CLKIN
frequency, the PLL needs time to
lock before the core can execute or begin the boot process. A delayed core
reset has been added via the delay circuit. There is a 12-bit counter that
Figure 15-3. Chip Reset Circuit
CLKIN
RESET
Delayed Internal
Core Processor
PLL
Core Reset Delay Circuit
CLKIN
CORE_RST
CLKIN
ENA_CLK
PLL_RESET
12-bit Counter
Count 4096 CLKIN Cycles
ENA_CNT
RESETOUT
PLL reset and PLL clock
input enable occur on the
rising edge of
RESET
Reset
Содержание ADSP-21261 SHARC
Страница 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Страница 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Страница 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Страница 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Страница 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...