10-2
MPC8240 Integrated Processor User’s Manual
I
2
C Interface Overview
•
Bus-busy detection
•
Programmable on-chip digital filter rejecting electrical spikes on the bus
•
Module reset through software
10.1.2 I
2
C Interface Signal Summary
The I
2
C interface uses the serial data (SDA) signal and serial clock (SCL) signal for data
transfer. All devices connected to these two signals must have open-drain or open-collector
outputs. A logical AND function is performed on both signals with external pull-up
resistors. Note that the signal patterns driven on SDA represent address, data, or read/write
information at different stages of the protocol.
Table 10-1 summarizes the two signals that comprise the I
2
C interface.
10.1.3 I
2
C Register Summary
There are five registers in the I
2
C unit that are used for the address, data, configuration,
control, and status of the I
2
C interface. These registers are located in the embedded utilities
memory block; see Section 3.4, “Embedded Utilities Memory Block (EUMB).” Table 10-2
summarizes the I
2
C registers. Complete descriptions of these registers are provided in
Section 10.3, “I2C Register Descriptions.”
Table 10-1. I
2
C Interface Signal Description
Signal Name
Idle State
I/O
State Meaning
SCL (serial clock)
HIGH
I
When the MPC8240 is idle or acts as a slave, SCL defaults as an input.
The unit uses SCL to synchronize incoming data on SDA. The bus is
assumed to be busy when SCL is detected low.
O
As a master, the MPC8240 drives SCL along with SDA when transmitting.
As a slave, the MPC8240 drives SCL low for data pacing.
SDA (serial data)
HIGH
I
When the MPC8240 is idle or in a receiving mode, SDA defaults as an
input. The unit receives data from other
I
2
C
devices on SDA. The bus is
assumed to be busy when SDA is detected low.
O
When writing as a master or slave, the MPC8240 drives data on SDA
synchronous to SCL.
Table 10-2. I
2
C Register Summary
Local Memory
Offset
Register Name
0x0_3000
I
2
C address register (I2CADR)
0x0_3004
I
2
C frequency divider register (I2CFDR)
0x0_3008
I
2
C control register (I2CCR)
0x0_300C
I
2
C status register (I2CSR)
0x0_3010
I
2
C data register (I2CDR)
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...