82802AB datasheet(17/53 Pages) INTEL

17 / 53 page

Intel

® 82802AB/AC Firmware Hub

Datasheet

Interface Operation Description

3.1.

Read

Memory information, identifier codes, GPI registers or the status register can be read, regardless of the

PP voltage. Commands using the read mode include: reading memory from the array, reading the

identifier codes, reading the status register, reading the lock bit registers, reading the random number

generator, reading the GPI registers, and reading the RNG status register. Upon initial device power-up

or after exit from reset, the device automatically resets to read array mode.

3.2.

Write

Writes to the memory array’s CUI are initiating by issuing a write through the Intel FWH interface. (See

the following information on timing and Intel FWH cycle write protocol specifics.) The CUI does not

occupy a single, specific memory location—any valid address may be given. However, certain

commands, such as block erase, require the address be within the range of the desired address block.

3.3.

Output Disable

When the Intel FWH is not selected through a FWH read or write cycle, the Intel FWH interface outputs

(FWH[3:0]) are disabled and is placed in a high-impedance state.

3.4.

Reset

RST# or INIT# at VIL initiates a device reset. In the read mode, RST# or INIT# low deselects the

memory, places output drivers in a high-impedance state, and turns off all internal circuits. RST# or

INIT# must be held low for time tPLPH (A/A Mux and FWH operation). The Intel FWH resets to read

array mode upon return from reset, and all blocks are set to default (locked) status (see 4.9.1), regardless

of their locked state prior to reset.

During block erase or program, driving RST# or INIT# low will abort the operation underway, in

addition to causing a reset latency. Memory contents being altered are no longer valid, since the data may

be partially erased or programmed.

It is important to assert RST# or INIT# during system reset. When the system comes out of reset, it will

expect to read from the memory array of the device. If a system reset occurs with no FWH reset—this is

hardware dependent—it is possible that proper processor initialization will not occur. (The Intel FWH

memory may be providing status information instead of memory array data.)

82802AB Datasheet(PDF) 17 Page - Intel Corporation