AS1108
Datasheet - Detailed Description
Shutdown Mode
The AS1108 features a shutdown mode, consuming only 10µA (max) current. Shutdown mode is entered via a write to
the Shutdown Register (see Table 8). At that point, all segment current sources are pulled to ground and all digit driv-
ers are connected to VDD, so that all segments are blanked.
Note: During shutdown mode the Digit-Registers maintain their data.
Shutdown mode can either be used as a means to reduce power consumption or for generating a flashing display
(repeatedly entering and leaving shutdown mode). For minimum supply current in shutdown mode, logic input should
be at GND or VDD (CMOS logic level).
The device needs typically 250µs to exit shutdown mode, and during shutdown mode the AS1108 is fully programma-
ble. Only the display test mode (see page 11) overrides shutdown mode.
When entering or leaving shutdown mode, the Feature Register is reset to its default values (all 0s) when Shutdown
Register bit D7 (page 10) = 0. When bit D7 = 1, the Feature Register is left unchanged when entering or leaving shut-
down mode.
Note: If the AS1108 is used with an external clock, Shutdown Register bit D7 should be set to 1 when writing to the
Shutdown Register.
Digit- and Control-Registers
The AS1108 contains four Digit-Registers and six control-registers, which are listed in Table 7. All registers are
selected using a 4-bit address word, and communication is done via the serial interface.
ꢀ
Digit Registers – These registers are realized with an on-chip 32-bit memory. Each digit can be controlled directly
without rewriting the whole register contents.
ꢀ
Control Registers – These registers consist of decode mode, display intensity, number of scanned digits, shut-
down, display test and features selection registers.
Table 7. Register Address Map
Address
Register
HEX Code
Page
D15:D12
D11
0
D10
0
D9
0
0
1
1
0
0
1
1
0
0
1
1
D8
0
1
0
1
0
1
0
1
0
1
0
1
No-Op
Digit 0
0xX0
0xX1
0xX2
0xX3
0xX4
0xX9
0xXA
0xXB
0xXC
0xXD
0xXE
0xXF
X
X
X
X
X
X
X
X
X
X
X
X
13
N/A
N/A
N/A
N/A
10
0
0
Digit 1
0
0
Digit 2
0
0
Digit 3
0
1
Decode-Mode
Intensity Control
Scan Limit
Shutdown
N/A
1
0
1
0
12
1
0
12
1
1
10
1
1
N/A
13
Feature
1
1
Display Test
1
1
11
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