
A49FL004
PRELIMINARY       (September, 2005, Version 0.0) 
6 
AMIC Technology, Corp.
FWH MODE SELECTION 
The A49FL004 can operate in two configurable interfaces: 
The In-System Hardware interface and Address/Address 
Multiplexed (A/A Mux) interface controlled by IC pin. If the IC 
pin is set to logic high (V
IH
), the devices enter into A/A Mux 
interface mode. If the IC pin is set logic low (V
IL
), the device 
will be in in-system hardware interface mode. During the in-
system 
hardware 
interface 
automatically detect the Firmware Hub (FWH) or Low Pin 
Count (LPC) memory cycle sent from host system and 
response to the command accordingly. The IC pin must be 
setup during power-up or system reset, and stays no change 
during device operation. 
mode, 
the 
device 
can 
When working in-system, typically on a PC or Notebook for 
Intel Platform, the A49FL004 enters into the FWH mode 
automatically. The device is configured to interface with its 
host using Intel’s Firmware Hub proprietary protocol.  
Communication between the host (Intel ICH) and the 
A49FL004 occurs via the 4-bit I/O communication signal, 
FWH[3:0] and FWH4. In A/A Mux mode, the device is 
programmed via 11-bit address A[10:0] and 8-pin data 
I/O[7:0] interfaces. The address inputs are multiplexed in row 
and column selected by column the control signal 
column addresses are mapped to the higher internal 
addresses, and the row addresses are mapped to the lower 
internal addresses. 
C
R/
. The 
FWH MODE OPERATION 
In FWH mode, the A49FL004 is connected through a 5-pin 
communication interface - FWH[3:0] and FWH4 pins to work 
with Intel Family of I/O Controller Hubs (ICH) chipset 
platforms. The FWH mode also supports JEDEC standard 
Software Data Protection (SDP) product ID entry, byte 
program, sector erase, and block erase command 
sequences. The chip erase command sequence is only 
available in A/A Mux mode.  
The addresses and data are transmitted through the 4-bit 
FWH[3:0] bus synchronized with the input clock on CLK pin 
during a FWH memory cycle operation. The address or data 
on FWH[3:0] bus is latched on the rising edge of the clock. 
The device enters standby mode when FWH4 is high and no 
internal operation is in progress. The device is in ready mode 
when FWH4 is low and no activity is on the bus. 
FWH Read Operation 
FWH Read Operations read from the memory cells or 
specific registers in the FWH device. A valid FWH Read 
operation starts when FWH4 is Low as CLK rises and a 
START value “1101b” is on FWH[3:0]. Addresses and data 
are transferred to and from the device decided by a series of 
“fields”. Field sequences and contents are strictly defined for 
FWH Read Operations. Refer to Table 2 for FWH Read 
Cycle definition. 
FWH Write Operation 
FWH Write operations write the FWH Interface or FWH 
registers. A valid FWH Write operation starts when FWH4 is 
Low as CLK rises and a START value “1110b” is on 
FWH[3:0]. Addresses and data are transferred to and from 
the device decided by a series of “fields”. Field sequences 
and contents are strictly defined for FWH Write operations. 
Refer to Table 3 for FWH Write Cycle Definition. 
FWH Abort Operation 
The FWH4 signal indicates the start of a memory cycle or the 
termination of a cycle in FWH mode. Asserting FWH4 for one 
or more clock cycle with a valid START value on FWH[3:0] 
will initiate a memory read or memory write cycle. If the 
FWH4 is driven low again for one or more clock cycles during 
this cycle, this cycle will be terminated and the device will 
wait for the ABORT command “1111b” to release the 
FWH[3:0] bus. If the abort occurs during the program or 
erase operation such as checking the operation status with 
Data
Polling (I/O
7
) or Toggle Bit (I/O
6
) pins, the read status 
cycle will be aborted but the internal program or erase 
operation will not be affected. Only the reset operation 
initiated by 
RST
  or INIT pin can terminate the program or 
erase operation. 
Response To Invalid Fields  
During FWH operations, the device will not explicitly indicate 
that it has received invalid field sequences. The response to 
specific invalid fields or sequences is as follows: 
Address out range: 
The FWH address sequence is 7 fields 
long (28 bits), but only the last five address fields (20 bits) 
will be decoded by A49FL004. Address A22 has the special 
function of directing reads and writes to the flash memory 
(A22=1) or to the register space (A22=0). 
Invalid IMSIZE Field: 
If the FWH device receives and invalid 
size field during a Read or Write operation, the device will 
reset and no operation will be attempted. The A49FL004 will 
not generate any kind of response in this situation. Invalid 
size field for a Read/Write cycles are anything but “0000b”.