BQ2024 Datasheet, PDF (13/19 Pages) Texas Instruments – 1.5K-BIT SERIAL EPROM WITH SDQ INTERFACE

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bq2024
SLUS770 – MAY 2007
PROGRAM PROFILE BYTE
The PROGRAM PROFILE byte is read to determine the WRITE MEMORY programming sequence required by
a specific manufacturer. After issuing a ROM command, the host issues the PROGRAM PROFILE BYTE
command, 99h. Figure 12 shows the the bq2024 responds with 55h. This informs the host that the WRITE
MEMORY programming sequence is the one described in the WRITE MEMORY command section of this data
sheet.
From ROM
Command
Program
N
Profile Command?
99h
Y
bq2024 Transmits
55h
Other
Command
Codes
Master Issues Reset
bq2024
is in
Reset State
Figure 12. PROGRAM PROFILE Command Flow
SDQ SIGNALING
All SDQ signaling begins with initializing the device, followed by the host driving the bus low to write a 1 or 0, or
to begin the start frame for a bit read. Figure 13 shows the initialization timing, whereas Figure 14 and Figure 15
show that the host initiates each bit by driving the DATA bus low for the start period, t_WSTRB / t_RSTRB. After the bit
is initiated, either the host continues controlling the bus during a WRITE, or the bq2024 responds during a
READ.
RESET AND PRESENCE PULSE
If the DATA bus is driven low for more than 120 µs, the bq2024 may be reset. Figure 13 shows that if the DATA
bus is driven low for more than 480 µs, the bq2024 resets and indicates that it is ready by responding with a
PRESENCE PULSE.
V_PU
V_IH
V_IL
RESET
(Sent by Host)
Presence Pulse
(Sent by bq2024)
t_RST
t_PPD
t_PP
t_RSTREC
Figure 13. Reset Timing Diagram
WRITE
The WRITE bit timing diagram in Figure 14 shows that the host initiates the transmission by issuing the t_WSTRB
portion of the bit and then either driving the DATA bus low for a WRITE 0, or releasing the DATA bus for a
WRITE 1.
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