Rainbow Electronics MAX1139 User Manual
Page 12
MAX1136–MAX1139
Slave Address
A bus master initiates communication with a slave device
by issuing a START condition followed by a slave
address. When idle, the MAX1136–MAX1139 continuous-
ly wait for a START condition followed by their slave
address. When the MAX1136–MAX1139 recognize their
slave address, they are ready to accept or send data.
The slave address has been factory programmed and is
always 0110100 for the MAX1136/MAX1137, and
0110101 for MAX1138/MAX1139 (Figure 7). The least sig-
nificant bit (LSB) of the address byte (R/W) determines
whether the master is writing to or reading from the
MAX1136–MAX1139 (R/W = 0 selects a write condition,
R/W = 1 selects a read condition). After receiving the
address, the MAX1136–MAX1139 (slave) issues an
acknowledge by pulling SDA low for one clock cycle.
Bus Timing
At power-up, the MAX1136–MAX1139 bus timing is set
for fast mode (F/S-mode) which allows conversion rates
up to 22.2ksps. The MAX1136–MAX1139 must operate
in high-speed mode (HS-mode) to achieve conversion
rates up to 94.4ksps. Figure 1 shows the bus timing for
the MAX1136–MAX1139’s 2-wire interface.
HS-Mode
At power-up, the MAX1136–MAX1139 bus timing is set
for F/S-mode. The bus master selects HS-mode by
addressing all devices on the bus with the HS-mode
master code 0000 1XXX (X = don’t care). After success-
fully receiving the HS-mode master code, the
MAX1136–MAX1139 issue a not-acknowledge allowing
SDA to be pulled high for one clock cycle (Figure 8).
After the not-acknowledge, the MAX1136–MAX1139 are
in HS-mode. The bus master must then send a repeated
START followed by a slave address to initiate HS-mode
communication. If the master generates a STOP condi-
tion the MAX1136–MAX1139 returns to F/S-mode.
2.7V to 3.6V and 4.5V to 5.5V, Low-Power,
4-/12-Channel, 2-Wire Serial 10-Bit ADCs
12
______________________________________________________________________________________
0
1
1
1
0
0
0
R/W
A
SLAVE ADDRESS
MAX1136/MAX1137
S
SCL
SDA
1
2
3
4
5
6
7
8
9
DEVICE
SLAVE ADDRESS
0110100
0110101
MAX1136/MAX1137
MAX1138/MAX1139
Figure 7. MAX1136/MAX1137 Slave Address Byte
0
0
0
1
0
X
X
X
A
HS-MODE MASTER CODE
SCL
SDA
S
Sr
F/S-MODE
HS-MODE
Figure 8. F/S-Mode to HS-Mode Transfer