DS90C3201_15 Datasheet, PDF (16/22 Pages) Texas Instruments – 3.3V 8 MHz to 135 MHz Dual FPD-Link Transmitter

DS90C3201
SNLS192D – APRIL 2005 – REVISED APRIL 2013
APPLICATION INFORMATION
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Two-Wire Serial Communication Interface Description
The DS90C3201 operates as a slave on the Serial Bus, so the S2CLK line is an input (no clock is generated by
the DS90C3201) and the S2DAT line is bi-directional. DS90C3201 has a fixed 7bit slave address. The address is
not user configurable in anyway.
A zero in front of the register address is required. For example, to access register 0x0Fh, “0F” is the correct way
of accessing the register.
COMMUNICATING WITH THE DS90C3201 CONTROL REGISTERS
There are 32 data registers (one byte each) in the DS90C3201, and can be accessed through 32 addresses. All
registers are predefined as read only or read and write. The DS90C3201 slave state machine does not require
an internal clock and it supports only byte read and write. Page mode is not supported. The 7-bit binary address
is 0111111 All seven bits are hardwired internally.
Reading the DS90C3201 can take place either of three ways:
1. If the location latched in the data register addresses is correct, then the read can simply consist of a slave
address byte, followed by retrieving the data byte.
2. If the data register address needs to be set, then a slave address byte, data register address will be sent
first, then the master will repeat start, send the slave address byte and data byte to accomplish a read.
3. When performing continuous read operations, another write (or read) instruction in between reads needs to
be completed in order for the two-wire serial interface module to read repeatedly.
The data byte has the most significant bit first. At the end of a read, the DS90C3201 can accept either
Acknowledge or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave
that the Master has read its last byte).
Bus Activity:
Master
Slave Address
SDA Line S
Bus Activity:
DS90C3201
AAA
2 1 00
AC
K
Register
Address
Slave Address
S
AC
K
AAA
2101
AC
K
AC
K
P
Data
Figure 17. Byte Read
The master must generate a Start by sending the 7-bit slave address plus a 0 first, and wait for acknowledge
from DS90C3201. When DS90C3201 acknowledges (the 1st ACK) that the master is calling, the master then
sends the data register address byte and waits for acknowledge from the slave. When the slave acknowledges
(the 2nd ACK), the master repeats the “Start” by sending the 7-bit slave address plus a 1 (indicating that READ
operation is in progress) and waits for acknowledge from DS90C3201. After the slave responds (the 3rd ACK),
the slave sends the data to the bus and waits for acknowledge from the master. When the master acknowledges
(the 4th ACK), it generates a “Stop”. This completes the “ READ”.
A Write to the DS90C3201 will always include the slave address, data register address byte, and a data byte.
Bus Activity:
Master
SDA Line
S
Bus Activity:
DS90C3201
16
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Slave
Address
AAA
2100
Register
Address
Data
P
AC
AC
AC
K
K
K
Figure 18. Byte Write
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