AM79C971VCW datasheet(100/265 Pages) AMD

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100

Am79C971

Other Data Registers

Other data registers are the following:

1. Bypass Register (1 bit)

2. Device ID register (32 bits) (Table 17).

The contents of the Device ID register is the same as

the contents of CSR88.

NAND Tree Testing

The Am79C971 controller provides a NAND tree test

mode to allow checking connectivity to the device on a

printed circuit board. The NAND tree is built on all PCI

bus, MII, and LED signals.

NAND tree testing is enabled by asserting RST. The re-

sult of the NAND tree test can be observed on the INTA

pin. See Figure 55.

Pin 143 (RST) is the first input to the NAND tree. Pin

145 (CLK) is the second input to the NAND tree, fol-

lowed by pin 147 (GNT). All other PCI bus, Expansion

Bus, MII, LED signals follow, counterclockwise, with pin

136 (EECS) being the last. Pins labeled NC, analog in-

terfaces, and all power supply pins are not part of the

NAND tree. Table 18 shows the complete list of pins

connected to the NAND tree.

RST must be asserted low to start a NAND tree test

sequence. Initially, all NAND tree inputs except RST

should be driven high. This will result in a high output

at the INTA pin. If the NAND tree inputs are driven from

high to low in the same order as they are connected to

build the NAND tree, INTA will toggle every time an ad-

ditional input is driven low. INTA will change to low,

when CLK is driven low and all other NAND tree inputs

stay high. INTA will toggle back to high, when GNT is

additionally driven low. The square wave will continue

until all NAND tree inputs are driven low. INTA will be

high, when all NAND tree inputs are driven low. See

Figure 56.

Note: Some of the pins connected to the NAND tree

are outputs in normal mode of operation. They must not

be driven from an external source until the Am79C971

controller is configured for NAND tree testing.

Figure 55.

NAND Tree Circuitry

Table 17.

Device ID Register

Bits 31-28

Version

Bits 27-12

Part Number (0010 0110 0010 0011)

Bits 11-1

Manufacturer ID. The 11 bit manufacturer ID

cod for AMD is 00000000001 in accordance

with JEDEC publication 106-A.

Bit 0

Always a logic 1

Am79C971

Core

RST (pin143)

CLK (pin 145)

VDD

GNT (pin 147)

EECS (pin 136)

INTA (pin 142)

MUX

....

INTA

20550D-58

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