Rainbow Electronics MAX6959 - Manual (Page 9)

Operation with Multiple Masters
If the MAX6958/MAX6959 are operated on a 2-wire
interface with multiple masters, a master reading the
MAX6958/MAX6959 should use a repeated start
between the write, which sets the MAX6958/MAX6959s’
address pointer, and the read(s) that takes the data
from the location(s) set by the address pointer. It is
possible for master 2 to take over the bus after master
1 has set up the MAX6958/MAX6959s’ address pointer
but before master 1 has read the data. If master 2 sub-
sequently changes the MAX6958/MAX6959s’ address
pointer, then master 1's delayed read may be from an
unexpected location.
Command Address Autoincrementing
Address autoincrementing allows the MAX6958/
MAX6959 to be configured with the shortest number of
transmissions by minimizing the number of times the
command byte needs to be sent. The address pointer
stored in the MAX6958/MAX6959 increments after each
data byte is written or read, unless the address equals
01111111 (Table 3).
Digit Type Registers
The MAX6958/MAX6959 store display data in five regis-
ters. The four digit registers each control the seven
numeric segments of a seven-segment digit, but not
the DP segments. The segments register controls eight
individual LEDs, which can be any mix of discrete LEDs
and any or all of the DP segments of the four 7-seg-
ment digits (Table 5) (Figure 10).
MAX6958/MAX6959
2-Wire Interfaced, 3V to 5.5V, 4-Digit,
9-Segment LED Display Drivers with Keyscan
_______________________________________________________________________________________ 9
COMMAND BYTE
ADDRESS RANGE
AUTOINCREMENT BEHAVIOR
00000000 to
01111110
Command byte address autoincrements
after byte read or written
01111111
Command byte address remains at
01111111 after byte written or read
Table 3. Command Address
Autoincrement Behavior
COMMAND ADDRESS
REGISTER
D15 D14 D13 D12 D11 D10 D9 D8
HEX
CODE
No-op 0 0 0 0 0 0 0 0 0x00
Decode mode 0 0 0 0 0 0 0 1 0x01
Intensity 0 0 0 0 0 0 1 0 0x02
Scan limit 0 0 0 0 0 0 1 1 0x03
Configuration 0 0 0 0 0 1 0 0 0x04
Factory reserved. Do not write to this register. 0 0 0 0 0 1 0 1 0x05
GPIO (MAX6959 only) 0 0 0 0 0 1 1 0 0x06
Display test 0 0 0 0 0 1 1 1 0x07
Read key debounced (MAX6959 only)
A write to this register is ignored.
0 0 0 0 1 0 0 0 0x08
Read key pressed (MAX6959 only)
A write to this register is ignored.
0 0 0 0 1 1 0 0 0x0C
Digit 0 0 0 1 0 0 0 0 0 0x20
Digit 1 0 0 1 0 0 0 0 1 0x21
Digit 2 0 0 1 0 0 0 1 0 0x22
Digit 3 0 0 1 0 0 0 1 1 0x23
Segments 0 0 1 0 0 1 0 0 0x24
Table 4. Register Address Map
a
b
c
d
e
f
g
dp
Figure 10. Segment Labeling for 7-Segment Display