Datasheet

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