AM79C972BVCW datasheet(89/130 Pages) AMD

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Am79C972

Other Data Registers

Other data registers are the following:

1. Bypass Register (1 bit)

2. Device ID register (32 bits) (Table 14).

Note: The content of the Device ID register is the

same as the content of CSR88.

NAND Tree Testing

The Am79C972 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, TBC_EN, and EAR pins.

NAND tree testing is enabled by asserting RST. PG

input should be driven HIGH during NAND tree testing.

All PCI bus signals will become inputs on the assertion

of RST. The result of the NAND tree test can be ob-

served on the INTA pin. See Figure 50.

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

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

lowed by pin 145 (GNT). All other PCI bus signals fol-

low, counterclockwise, with pin 129 (EAR) being the

last. Table 15 shows the complete list of pins connected

to the NAND tree.

RST must be asserted low to start a NAND tree test se-

quence. 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 51.

Some of the pins connected to the NAND tree are out-

puts in normal mode of operation. They must not be

driven from an external source until the Am79C972

controller is configured for NAND tree testing.

Figure 50.

NAND Tree Circuitry

Table 14.

Device ID Register

Bits 31-28

Version

Bits 27-12

Part Number (0010 0110 0010 0100)

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

Am79C972

Core

RST (pin143)

CLK (pin 144)

VDD

GNT (pin 145)

EAR (pin 129)

INTA (pin 142)

MUX

....

INTA

21485C-53

AM79C972BVCW Datasheet(PDF) 89 Page - Advanced Micro Devices

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