8 Mbit Firmware Hub
SST49LF008A
Data Sheet
TABLE 4: FWH Write Cycle
Clock
Cycle
Field
Name
Field Contents
FWH[3:0]1
FWH[3:0]
Direction
Comments
1
START
1110
IN
FWH4 must be active (low) for the part to respond.
Only the last start field (before FWH4 transitions high)
should be recognized. The START field contents indi-
cate a FWH memory Read cycle.
2
IDSEL
0000 to 1111
IN
Indicates which SST49LF008A device should
respond. If the IDSEL (ID select) field matches the
value ID[3:0], then that particular device will respond
to the whole bus cycle.
3-9
10
IMADDR
IMSIZE
DATA
YYYY
0000 (1 byte)
YYYY
IN
IN
IN
These seven clock cycles make up the 28-bit memory
address. YYYY is one nibble of the entire address.
Addresses are transferred most-significant nibble first.
This size field indicates how many bytes will be
transferred during multi-byte operations. The FWH
only supports single-byte writes. IMSIZE=0000b
11
This field is the least-significant nibble of the data byte.
This data is either the data to be programmed into the
flash memory or any valid flash command.
12
13
DATA
TAR0
YYYY
1111
IN
This field is the most-significant nibble of the data byte.
IN then Float
In this clock cycle, the master (Intel ICH) has driven the
then float bus to all ‘1’s and then floats the bus prior to
the next clock cycle. This is the first part of the bus
“turnaround cycle.”
14
TAR1
1111 (float)
Float then OUT The SST49LF008A takes control of the bus during this
cycle. During the next clock cycle it will be driving the
“sync” data.
15
16
RSYNC
TAR0
0000
1111
OUT
The SST49LF008A outputs the values 0000, indicating
that it has received data or a flash command.
OUT then Float In this clock cycle, the SST49LF008A has driven the
bus to all then float ‘1’s and then floats the bus prior to
the next clock cycle. This is the first part of the bus
“turnaround cycle.”
17
TAR1
1111 (float)
Float then IN
The master (Intel ICH) resumes control of the bus during
this cycle.
T4.4 1161
1. Field contents are valid on the rising edge of the present clock cycle.
CLK
FWH4
STR
IDS
IMADDR
IMS
DATA
TAR
RSYNC
TAR
FWH[3:0]
1161 F10.0
FIGURE 7: Write Waveforms
©2006 Silicon Storage Technology, Inc.
S71161-11-000
3/06
13
SST [ SILICON STORAGE TECHNOLOGY, INC ]
