N34TS04
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6
SPD EEPROM Bank Selection
Upon power−up, the address pointers for both the
Temperature Sensor (TS) and on−board EEPROM are
initialized to 00h. The TS address pointer will thus point to
the Capability Register and the EEPROM address pointer
will point to the first location in the lower 2−Kb bank (SPD
page 0).
Only one SPD page is visible (active) at any given time.
The lower SPD page is automatically selected at power−up.
The upper SPD page can be activated (and the lower one
implicitly de−activated) by executing the SPA1 utility
command. The SPA0 utility command can then be used to
re−activate the lower SPD page without powering down.
The identity of the active SPD page can be retrieved with the
RPA command.
SPD page selection related command details are
presented in Table 9c, Table 9d, Figure 13 and Figure 14.
Write Operations
EEPROM Byte and TS Register Write
To write data to a TS register, or to the on−board
EEPROM, the Master creates a START condition on the bus,
and then sends out the appropriate Slave address (with the
R/W
bit set to ‘0’), followed by a starting data byte address
or TS register address, followed by data. The matching
Slave will acknowledge the Slave address, EEPROM byte
address or TS register address and the data byte(s), one for
EEPROM data (Figure 6) and two for TS register data
(Figure 7). The Master then ends the session by creating a
STOP condition on the bus. The STOP completes the
(volatile) TS register update or starts the internal Write cycle
for the (non−volatile) EEPROM data (Figure 8).
EEPROM Page Write
Each of the two 2−Kb banks is organized as 16 pages of
16 bytes each (not to be confused with the SPD page, which
refers to the entire 2−Kb bank). One of the 16 memory pages
is selected by the 4 most significant bits of the byte address,
while the 4 least significant bits point to the byte position
within the page. Up to 16 bytes can be written in one Write
cycle (Figure 9).
During data load, the internal byte position pointer is
automatically incremented after each data byte is loaded. If
the Master transmits more than 16 data bytes, then earlier
data will be replaced by later data in a ‘wrap−around’
fashion within the 16−byte wide data buffer. The internal
Write cycle then starts following the STOP.
Acknowledge Polling
Acknowledge polling can be used to determine if the
N34TS04 is busy writing to EEPROM, or is ready to accept
commands. Polling is executed by interrogating the device
with a ‘Selective Read’ command (see READ
OPERATIONS). The N34TS04 will not acknowledge the
Slave address as long as internal EEPROM Write is in
progress.
Delivery State
The N34TS04 is shipped ‘unprotected’, i.e. none of the
Software Write Protection (SWP) flags is set. The entire
memory is erased, i.e. all bytes are 0xFF.
Read Operations
Immediate Read
A N34TS04 presented with a Slave address containing a
‘1’ in the R/W
position will acknowledge the Slave address
and will then start transmitting SPD data or respectively TS
register data from the current address pointer location. The
Master stops this transmission by responding with NoACK,
followed by a STOP (Figures 10a, 10b).
Selective Read
The Read operation can be started from a specific address,
by preceding the Immediate Read sequence with a ‘data less’
Write sequence. The Master sends out a START, Slave
address and byte or register address, but rather than
following up with data (as in a Write operation), the Master
then issues another START and continuous with an
Immediate Read sequence (Figures 11a, 11b).
Sequential EEPROM Read
EEPROM data can be read out indefinitely, as long as the
Master responds with ACK (Figure 12). The internal address
pointer is automatically incremented after every data byte
sent to the bus. If the end of the active 2−Kb bank is reached
during continuous Read, then the address count
‘wraps−around’ to the beginning of the active 2−Kb bank,
etc. Sequential Read works with either Immediate Read or
Selective Read, the only difference being that in the latter
case the starting address is intentionally updated.
Figure 6. EEPROM Byte Write
BYTE
ADDRESS
SLAVE
SPD
ADDRESS
S
A
C
K
A
C
K
DATA
A
C
K
S
T
O
P
P
BUS ACTIVITY:
MASTER
SLAVE
SDA LINE
S
T
A
R
T
