DA8444A.005
May 31, 1996
FUNCTIONS
d
Address Byte
Valid addresses are 40, 42, 44, 46, 48, 4A, 4C,
4E(hex), depending on the programming of bits A2, A1
and A0. With these addresses, up to eight MAS8444A
ICs can be operated independently from one I
2
C-bus.
No other addresses are acknowledged by the
Instruction and data bytes
Valid instructions from 00 to 0F and F0 to FF (hex);
MAS8444A will not respond to other instruction value,
but will still generate an acknowledgement. Instructions
00 to0F cause auto-incrementing of the sub-address
(bits SD to SA) when more than one data byte is sent
within one transmission. With auto-incrementing, the
first data byte is written into the DAC addessed by bits
SD to SA and then the sub-address is automatically
I
2
C - bus
Input SCL (pin 4) and input/output SDA (pin 3) conform
to I
2
C-bus specifications. Pins 3 and 4 are protected
against voltage pulses by internal zener diodes
Input Vmax
Input Vmax (pin 2) provides a means of comprising the
output voltage swing of the DACs. The maximum DAC
output voltage is restricted to approximately
MAS8444A. The address inputs A0, A1 and A2 are
programmed by connection to GND for An = 0 or to
VDD for An = 1. If the inputs are left floating, An = 1 will
result. For MAS8444AS, A2 is always 1.
incremented by one position for the next databyte in
the series. Auto-incrementing does not occur with
instructions F0 to FF. Valid sub-addresses (bits SD to
SA) are 0 to 7 (hex) relating numerically to DAC0 to
DAC7. When the auto-incrementing function is used,
the sub-address will sequence through all possible
values (0 to F, 0 to F, etc.). While the sub-address is
between 8 and F no DAC outputs change.
connected to the ground plane and therefore the
normal bus line voltage shall not exceed 5.5v.
Vmax+VDACmin while the 6-bit resolution is
maintained, therefore giving a finer voltage resolution
of smaller output swings.
6
MAS [ MICRO ANALOG SYSTEMS ]
