Cypress Semiconductor ISR 37000 CPLD Especificaciones descargar pdf (Pagina 10)

Design Considerations for ISR Programming of Cypress CPLDs

The value of this pull-down resistor for TCK is not crucial since

the external JTAG pin driver simply has to be strong enough

to overpower the resistor. Typical values are 10 kΩ or 4.7kΩ.

LASH

370i Family

Like the Ultra37000 family, F

LASH

370i CPLDs have a separate

I/O power supply, V

CCIO

, which can support 5V or 3.3V levels.

Only the ISRPCCABLE can program an ISR chain containing

LASH

370i devices. This is because this cable alone produces

the required 12V supervoltage on the ISRen pin required for

device programming. This cable, however, does not support

3.3V ISR signaling so it cannot be used with any 3.3V ISR

device like the Delta39K.

Smaller F

LASH

370i packages contain pins which offer dual-

mode functionality between ISR programming mode and nor-

mal I/O mode, similar to the Ultra37000 family. The necessary

external logic to support dual functionality is detailed in Ap-

pendix A. Specific design considerations with cascading sin-

gle- and dual-function Ultra37000 and F

LASH

370i devices are

found in Appendix B.

Additional F

LASH

370i device and board-level design consider-

ations are found in Appendix C.

State of General Cypress ISR Device I/Os at Power-Up

When ISR devices are shipped from Cypress, the devices

have already been programmed, erased, and programmed

again as part of the testing process. They will not, therefore,

be blank when they first come out of the tube. They will, how-

ever, be programmed such that all of the I/Os are three-stated

after power-up. Furthermore, all I/Os (except TDO) are three-

stated during device programming. This allows soldering of

ISR devices directly onto a user’s board without having to

erase them first. It allows the user to power-up a board and

program the ISR devices on it without worrying whether their

initial, non-blank state will cause any problems such as output

contention with other devices on the board.

The ISR programming procedure is to take ISR devices di-

rectly from the tube, solder them onto the board, connect the

programming source (such as the ISR programming cable

attached to a PC), turn on the power to the board, and then

program the devices for the first time. Since many of the I/Os

on the ISR device(s) are undoubtedly inputs, other devices on

the board could be driving those pins immediately upon pow-

ering up the system. By having all of the ISR I/Os initially

programmed to be three-stated, and by guaranteeing the

same three-state during ISR programming, you are assured

that the ISR device will not also drive those pins. This pre-

vents bus contention, and prevents the ISR devices or other

devices on the board from being damaged. ISR devices can

be programmed for the first time in-system without fear that

other board components driving the CPLD will negatively ef-

fect operation.

As previously discussed, all ISR device I/Os will initially three-

state after first power-up regardless of whether the CPLD

contains volatile or non-volatile configuration bits.

Summary

The In-System Reprogrammable feature of Cypress ISR de-

vices provides the critical capability to manipulate program-

mable device configuration without the need to desolder com-

ponents from a user’s board. With a good understanding of

ISR design considerations involved and adherence to the rec-

ommended layout and termination practices, a printed circuit

board designer can implement a reliable method for device

reconfiguration or in-system test using boundary scan.

The Cypress ISR PC programming cables provide the sim-

plest method to build In-System Reprogrammability of pro-

grammable devices into systems. In-System Reprogramma-

bility (ISR) of a programmable device has several benefits. It

allows engineering development and debugging to occur

without having to socket the ISR devices and without having

to remove them and reprogram them in a device programmer.

This saves time regardless of the package type used. ISR is

especially valuable when fine-pitch packages like TQFPs and

FBGAs are used. This not only saves time, it can also avoid

the high likelihood of bending leads on very fine-leaded de-

vices. Also, by allowing soldering of TQFP packages directly

onto a board without sockets, it helps to avoid spending time

simply checking device-to-socket-lead connections during

debugging. ISR also allows for designs which can be recon-

figured in the field, either by a software update or by other

input from the system. The superior routability and flexible

architecture of the Cypress ISR CPLDs enhance the value of

all of these benefits greatly by allowing design changes to be

made during prototyping, debugging, or field operation and

still successfully route to the already-defined pinout, even on

designs that utilize most or all of the device’s resources.

This application note explains the available Cypress program-

ming cables and the signals they use, and also covers many

design techniques and considerations that show how to easily

use the capabilities of ISR devices. These include: descrip-

tion of the logic needed when using the dual-function pins on

applicable ISR devices, connecting ISR devices in a program-

ming chain, and ISR differences between the programmable

logic device families.

Designing a daisy-chain of ISR devices is straightforward pro-

vided that the designer follows the layout guidelines set forth

in this document. By following the recommended layout prac-

tices, board-level problems will be eliminated and a highly

reliable programming method results.

References

1. Cypress Application Note. “System Design Considerations

When Using Cypress CMOS Circuits,” 1993.

2. IEEE Std 1149.1-1990 Test Access Port and Boundary

Scan Architecture, IEEE Computer Society, May 1990.

3. Johnson, H. and Graham M. “High-Speed Digital Design,”

Prentice-Hall, Inc., 1993.

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 19 20

Comentarios a estos manuales

Sin comentarios

Cypress Semiconductor ISR 37000 CPLD Especificaciones Pagina 10

Comentarios a estos manuales

Relacionado con productos y manuales para No Cypress Semiconductor ISR 37000 CPLD