DAC1220
SBAS082G –FEBRUARY 1998–REVISED SEPTEMBER 2009...................................................................................................................................... www.ti.com
PROGRAMMING
Commands
Communication with the DAC1220 consists entirely of
commands, which access the DAC1220 registers.
Commands consist of a command byte followed by
one, two or three data bytes. The data bytes can be
sent to the DAC1220 or read from the DAC1220,
depending on whether the command is a read
command or a write command.
Registers
There are four registers in the DAC1220, as shown in
the register map in Table 11. The Data Input Register
(DIR) and the two calibration registers are 24 bits in
length, and the Command Register (CMR), which
contains configuration bits, is 16 bits in length.
The format of the command byte is shown in Table 6,
and the bits are described in Table 7. DAC1220
commands access the register map, which is shown
in Table 11. A DAC1220 command can read or write
one byte, or two or three adjacent bytes, in the
register map.
Modes
The DAC1220 has three operating modes: Sleep,
Normal, and Self Calibration.
In Sleep mode, the DAC1220 output is off (high
impedance), and much of the internal circuitry is
switched off. In this mode the DAC1220 draws little
power. The oscillator continues to run, however.
Sleep is the mode entered after reset.
Bit and Byte Order
The order of the bits of data bytes in a command is
configurable. The DAC1220 can be programmed to
output data bytes MSB first or LSB first. The
command byte is always transmitted MSB first. See
the description of the MSB bit in Table 6 for further
details. The order of the data bytes themselves is
also configurable. See the description of the BD bit in
Table 13 for details. Note that the BD bit does not
affect the command byte; this always comes first.
In Normal mode, the DAC1220 is fully active, and the
output is on.
In Self Calibration mode, the DAC1220 runs its
self-calibration sequence. After the sequence is
complete, the DAC1220 switches to Normal mode.
See the Calibration section for more information.
Table 6. Command Byte Format
7
6
5
4
3
2
1
0
R/W
MB
0
ADR
Table 7. Command Byte Bits
BIT(S)
NAME
VALUE
DESCRIPTION
7
R/W
0
1
Write to register map
Read from register map
Number of bytes to read or write
1 byte
6–5
MB
00b
01b
10b
11b
0–15
2 bytes
3 bytes
Reserved; do not use
Start address in register map
3–0
ADR
12
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