
PRODUCT SPECIFICATION
16-1
I
2
C Interface
Chapter 16
by Essam Abu-ghoush, Robert Nichols
16.1
I
2
C OVERVIEW
TM1300 includes an
I
2
C
interface which can be used to
control many different multimedia devices such as:
DMSDs - Digital multi-standard decoders
DENCs - Digital encoders
Digital cameras
I
2
C - Parallel I/O expanders
The key features of the
I
2
C
interface are:
Supports I
2
C single master mode
I
2
C data rate up to 400 kbits/sec
Support for the 7-bit addressing option of the I
2
C
specification
Provisions for full software use of I
2
C interface pins
for implementing software I
2
C or similar protocols
Note that the I
2
C pins are also used to load the initial boot
parameters and/or code from a serial EEPROM as de-
scribed in
Section 13, “System Boot”
. The boot logic is
only active upon TM1300 hardware reset and quiescent
afterwards.
A typical system using the
I
2
C
interface is presented in
Figure 16-1
. The TM1300 is connected as a master to a
series of slave devices through SCL and SDA. Note that
the bus has one pullup resistor for each of the clock and
data lines. The pullup should be set to a voltage no high-
er than VREF_PERIPH.
16.2
NEW IN TM1300
The following are the main
I
2
C
differences from TM1000:
The SEX bit is removed. Endian-ness is fixed.
The
I
2
C
clock rate is closer to 100/400 kHz
The GDI bit now correctly indicates write-completion
Clock stretching is always enabled.
16.3
EXTERNAL INTERFACE
The
I
2
C
external interface is composed of two signals as
shown in
Table 16-1
.
16.4
I
2
C REGISTER SET
The
I
2
C
user interface consists of four registers visible to
the programmer. The registers are mapped into the
MMIO address space and are fully accessible to the pro-
grammer.
Figure 16-2
shows the
I
2
C
register set. To en-
sure compatibility with future devices, any undefined
MMIO bits should be ignored when read, and written as
‘0’s.
16.4.1
The IIC_AR is the I
2
C
address register and is used in both
master receive and transmit modes. This register is writ-
ten with the address(es) of the
I
2
C
slave device and the
bytecount for transmit/receive.
Table 16-2
lists the bit-
field definitions for the IIC_AR register.
IIC_AR Register
ADDRESS must be programmed to contain the 7 bits of
the desired slave address
The DIRECTION bitfield controls read/write operation on
the
I
2
C
interface. The bit definition is:
DIRECTION = 0 –> I
2
C write
Figure 16-1. Typical I
2
C system implementation
SCL
SDA
TM1300
Slave
I
2
C
Slave
I
2
C
+ VREF_PERIPH
R
p
R
p
Table 16-1. I
2
C External interface
Signal
Type
Description
IIC_SDA
I/O
I
2
C serial data
I
2
C
clock
IIC_SCL
O
Table 16-2. IIC_AR Register
Bits
Field Name
Definition
31:25
24
23:16
15:8
7:0
ADDRESS
DIRECTION
reserved
COUNT
reserved
7-bit slave device address.
Read/Write control bit
must be written to ‘0’
Byte count of requested transfer
Read as ‘0’