Cypress Semiconductor ISR 37000 CPLD Especificaciones descargar pdf (Pagina 17)

Design Considerations for ISR Programming of Cypress CPLDs

Appendix B. Simple Cascading Considerations for Ultra37000 and F

LASH

370i CPLDs

You can cascade many ISR devices in a system. That is, you

can daisy-chain the devices together and connect their pro-

gramming pins in such a way that the devices can be pro-

grammed from a single connection to the ISR programming

cable.

Cascading Single-Function ISR Devices or Dual-Function

Devices in Single-Function Mode

To do this, you simply tie all of the JTAGen, TCK and TMS pins

of each device to those same pins, respectively, on all of the

other devices, and then connect them to the corresponding

pins of the ISR cable connector. You then connect the TDI pin

from the cable connector to the TDI pin of the first device in

the chain, then connect the TDO output of that device to the

TDI input of the next device in the chain, then connect the

TDO output of that device to the TDI input of the next device

in the chain, and so forth, until you finally connect the TDO

output of the last device in the chain to the TDO pin of the

cable connector (see Figure 21). In Figure 21 many of the

Ultra37000 devices are single-function mode devices, there-

fore the JTAGen pin does not exist at all for these devices.

Cascading Dual-Function ISR Devices in Dual-Function

Mode

In addition to the extra circuitry needed for the dual-function

pins per ISR device, the JTAGen pin must also be connected

differently on the Ultra37000 devices than the F

LASH

370i de-

vices. This is necessary because of its different functionality

with a TTL HIGH input level as previously mentioned. This is

explained further in the rest of this application note. Figure 24

shows an example of two dual-function mode devices operat-

ing in dual-function mode on the TMS signal of two of the

three devices in the chain.

Driving the JTAGen Pin on the Ultra37000 Dual-Function

Mode Devices When Being Used in Single-Function Mode

Figure 21 shows that the user does not need to worry about

driving the JTAGen pin to a particular level if the JTAG pins

are only used for ISR operations. This example shows that it

is possible for the dual-function pins to operate in the I/O

mode for the Ultra37256 device when the ISR programming

cable is removed since a TTL LOW level could exist on the

JTAGen pin. Observation of Figure 21 shows that I/O conten-

tion problems are possible through the ISR connections from

one ISR device to another if multiple Ultra37000 devices were

connected in the same chain and the JTAG pins are used in

their I/O function. Output contention between devices is not a

problem if the output from all devices is the same polarity.

When and if further ISR operations need to be performed the

ISR cable drives the JTAGen pin HIGH which three-states the

I/O function and re-selects the JTAG function on the dual-

function pins so there is no contention problem possible be-

tween the ISR device and the ISR cable.

Driving the JTAGen Pin on the Ultra37000 Dual-Function

Mode Devices When Being Used in Dual-Function Mode

In many designs the user will elect to either use a single-

function mode Ultra37000 device or use a dual-function mode

Ultra37000 device in single-function mode. For these cases

the user can ignore the following discussion. Similar to the

LASH

370i family of devices, a TTL LOW level on the JTAGen

pin enables the I/O functionality of the Ultra37000 dual-func-

Figure 21. Simple Cascading Example - Single-Function Mode Operation

ISR Programming

Cable Connector

JTAGen

TDI

TDO

TCK

TMS

CY7C374i

PLCC

Ultra37512

BGA

JTAGen

TDI

TDO

TCK

TMS

Ultra37256

TQFP

TDI

TDO

TCK

TMS

ISRen

TDI

TDO

TCK

TMS

1 2 ... 12 13 14 15 16 17 18 19 20

Comentarios a estos manuales

Sin comentarios

Cypress Semiconductor ISR 37000 CPLD Especificaciones Pagina 17

Comentarios a estos manuales

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