PRELIMINARY DATA SHEET
MSP 34x1G
3. Control Interface
performed some other function (for example, servicing
an internal interrupt), it will hold the clock line I2C_CL
LOW to force the transmitter into a wait state. The
positions within a transmission where this may happen
are indicated by ’Wait’ in section 3.1.3. The maximum
wait period of the MSP during normal operation mode
is less than 1 ms.
3.1. I2C Bus Interface
3.1.1. Device and Subaddresses
The MSP 34x1G is controlled via the I2C bus slave
interface.
The IC is selected by transmitting one of the
MSP 34x1G device addresses. In order to allow up to
three MSP ICs to be connected to a single bus, an
address select pin (ADR_SEL) has been implemented.
With ADR_SEL pulled to high, low, or left open, the
MSP 34x1G responds to different device addresses. A
device address pair is defined as a write address (80,
84, or 88 hex) and a read address (81, 85, or 89 hex)
(see Table 3–1).
Internal hardware error handling:
In case of any internal hardware error (e.g. interruption
of the power supply of the MSP), the MSP’s wait
period is extended to 1.8 ms. After this time period
elapses, the MSP releases data and clock lines.
Indication and solving of the error status:
Writing is done by sending the device write address,
followed by the subaddress byte, two address bytes,
and two data bytes. Reading is done by sending the
write device address, followed by the subaddress byte
and two address bytes. Without sending a stop condi-
tion, reading of the addressed data is completed by
sending the device read address (81, 85, or 89 hex)
and reading two bytes of data. Refer to section 3.1.3.
for the I2C bus protocol and to section “Programming
Tips” on page 44 for proposals of MSP 34x1G I2C tele-
grams. See Table 3–2 for a list of available subad-
dresses.
1. MSP 34x1G-versions until A1: To indicate the
error status, all further acknowledge bits will be left
high. The MSP can then be reset by transmitting the
reset condition to CONTROL while ignoring the miss-
ing acknowledge bits.
2. MSP 34x1G-versions from A2 on: To indicate the
error status, the remaining acknowledge bits of the ac-
tual I2C-protocol will be left high. Additionally, bit[14] of
CONTROL is set to one. The MSP can then be reset
via the I2C bus by transmitting the reset condition to
CONTROL.
Besides the possibility of hardware reset, the MSP can
also be reset by means of the RESET bit in the CON-
TROL register by the controller via I2C bus.
Indication of reset (only versions from A2 on):
Any reset, even caused by an unstable reset line etc.,
is indicated in bit[15] of CONTROL.
Due to the internal architecture of the MSP 34x1G, the
IC cannot react immediately to an I2C request. The
typical response time is about 0.3 ms. If the MSP can-
not accept another complete byte of data until it has
A general timing diagram of the I2C bus is shown in
Fig. 4–25 on page 68.
MICRONAS INTERMETALL
17
MICRONAS [ MICRONAS ]
