MAX6956
quently changes, the MAX6956’s address pointer, then
master 1’s delayed read may be from an unexpected
location.
Command Address Autoincrementing
Address autoincrementing allows the MAX6956 to be
configured with the shortest number of transmissions
by minimizing the number of times the command
address needs to be sent. The command address
stored in the MAX6956 generally increments after each
data byte is written or read (Table 4).
Initial Power-Up
On initial power-up, all control registers are reset, the
current registers are set to minimum value, and the
MAX6956 enters shutdown mode (Table 6).
LED Current Control
LED segment drive current can be set either globally or
individually. Global control simplifies the operation
when all LEDs are set to the same current level,
because writing just the global current register sets the
current for all ports configured as LED segment drivers.
It is also possible to individually control the current
drive of each LED segment driver. Individual/global
brightness control is selected by setting the configura-
tion register I bit (Table 9). The global current register
(0x02) data are then ignored, and segment currents are
set using register addresses 0x12 through 0x1F (Tables
12, 13, and 14). Each segment is controlled by a nibble
of one of the 16 current registers.
Transition (Port Data Change) Detection
Port transition detection allows any combination of the
seven ports P24–P30 to be continuously monitored for
changes in their logic status (Figure 11). A detected
change is flagged on the transition detection mask reg-
ister INT status bit, D7 (Table 15). If port P31 is config-
ured as an output (Tables 1 and 2), then P31 also
automatically becomes an active-high interrupt output
(INT), which follows the condition of the INT status bit.
Port P31 is set as output by writing bit D7 = 0 and bit
D6 = 1 to the port configuration register (Table 1). Note
that the MAX6956 does not identify which specific
port(s) caused the interrupt, but provides an alert that
one or more port levels have changed.
2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or
28-Port LED Display Driver and I/O Expander
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