Datasheet
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MAX9257A/MAX9258A
Fully Programmable Serializer/Deserializer
with UART/I
2
C Control Channel
Read Packet
The ECU writes the sync frame, 7-bit device address plus
read/write bit (R/W = 1 for read), 8-bit register address,
and number of bytes to be read. The addressed device
responds with read data bytes (Figure 29). UART read
delay is maximum 4 bit times when reading from the
MAX9257A or the MAX9258A.
Time Between Frames
Up to two high bit times are allowed between frames.
Reset of Packet Boundary
A high time ranging from 14 UART bit times or more
resets the packet boundary. In this case, the next frame
received is assumed to belong to a new packet by
the MAX9257A/MAX9258A and UART-to-I
2
C converter.
Resetting the boundary is required. Not resetting the
boundary treats the following packets as part of the first
packet, and they may be processed incorrectly.
Data Rate
The control channel data rate in base mode is between
95kbps to 4.25Mbps (Table 28). In bypass mode, the
allowed data rate is DC to 10Mbps (Table 29). For data
rates faster than 4.25Mbps in bypass mode, REG8[5]
in MAX9257A and REG7[5] in MAX9258A must be set
high. Set the control channel data rate in base mode by
writ ing to REG8[1:0] in the MAX9257A and REG7[1:0] in
the MAX9258A. These write commands take effect in the
next control channel.
Programming the FAST bit takes effect in the same con-
trol channel. Both the MAX9257A and the MAX9258A
should have the same settings for FAST. It is recom-
mended to first program the FAST bit in the MAX9257A.
Programming FAST to 1 results in shorter UART pulses
on the differential link.
MAX9257A/MAX9258A
Device Address Programming
The MAX9257A/MAX9258A have device addresses that
can be programmed to any 7-bit address. Table 30
shows the default addresses.
Figure 29. UART Read Packet
Table 28. Control Channel Data Rate in
Base Mode
Table 29. Control Channel Data Rate in
Bypass Mode
Table 30. Default Device Address
MAX9257A REG8[1:0]
MAX9258A REG7[1:0]
RANGE
00
95kbps–400kbps
(default)
01 400kbps–1Mbps
10 1Mbps–4.25Mbps
11 1Mbps–4.25Mbps
MAX9257A REG8[5]
MAX9258A REG7[5]
RANGE
0 DC–4.25Mbps
1 4.25Mbps–10Mbps
DEVICE
DEFAULT
BINARY HEX
MAX9257A 1111 1010 0xFA
MAX9258A 1111 1000 0xF8
NUMBER OF BYTES
REG ADDRESS
BYTE 1
BYTE N
DEV ADDR +
R/W
SYNC