Rainbow Electronics MAX9258 - Manual (Page 27)

The LOCK and ERROR outputs can be wired in an
AND configuration if you have multiple serializers and
deserializers, or a single serializer fanned out to multi-
ple deserializers through a repeater. For such situa-
tions, wire the multiple LOCK outputs together and use
a single pullup resistor to pull up all the lines high.
LOCK is high if all the devices are locked. Do the same
thing for
ERROR; ERROR is low if any MAX9258 reports
errors.
Base Mode and Bypass Mode (Basics)
In the control channel phase, there are two modes: base
and bypass. In base mode, ECU always communicates
using the MAX9257/MAX9258 UART protocol and com-
munication with a peripheral device is performed in I
2 C
by the MAX9257. Packets not addressed to the
MAX9257 or the MAX9258 get converted to I
2 C and
passed to the peripheral device. Similarly, I 2 C packets
from the peripheral device get converted to UART pack-
ets in the reverse direction. ECU can disable communi-
cation to the peripheral device by writing a 0 to INTEN
(REG8[6] in the MAX9257 and REG7[6] in the MAX9258).
Base mode is the default mode. Bypass mode is entered
by writing a 0 to INTMODE and 1 to INTEN (Table 23).
Bypass mode is exited if there is no activity from ECU in
the control channel for the duration of CTO. When CTO
times out, INTEN reverts back to 0 and MAX9257/
MAX9258 revert back to base mode. To permanently
stay in bypass mode, ECU can lock the CTO timer or
program CTO to be longer than ETO and STO.
Timers
The MAX9257/MAX9258 feature three different timers.
The start timeout (STO) and end timeout (ETO) control
the duration of the control channel. The come-back
timeout (CTO) controls the duration of bypass mode.
STO Timer
The STO (start timeout) timer closes the control channel if
the ECU does not start using the control channel within
the STO timeout period. The STO timer is configured by
MAX9257/MAX9258
______________________________________________________________________________________ 27
Fully Programmable Serializer/Deserializer
with UART/I
2
C Control Channel
REG12[7:5] PREEMPHASIS (%)
000,101,110 20
001 40
010 60
011 80
100 100
111 0
Table 21. Preemphasis
PARALLEL-WORD
WIDTH (N)
GPIOs AVAILABLE
18 GPIO[8:9]
16 GPIO[6:9]
14 GPIO[4:9]
12 GPIO[2:9]
10 GPIO[0:9]
Table 22. GPIOs vs. Parallel-Word Width
INTEN
MAX9257 REG8[6],
MAX9258 REG7[6]
INTMODE
MAX9257 REG8[7],
MAX9258 REG7[7]
MODE
0 X
Base mode,
communication
with peripheral is
not enabled
1 1
Base mode,
communication
with peripheral is
enabled (I
2 C)
1 0
Bypass mode,
communication
with MAX9257/
MAX9258 is not
enabled,
communication
with peripheral is
enabled (UART)
Table 23. Selection of Base Mode or
Bypass Mode
REG2[7:4] STODIV
00XX 16
0100 16
0101 32
0110 64
0111 128
1000 256
1001 512
1010 1024
1011 2048
1100 4096
1101 8192
1110 16,384
1111 32,768
Table 24. STO Clock Divide Ratio