MC908AP8CFBE Datasheet, PDF (232/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Multi-Master IIC Interface (MMIIC)
14.3 I/O Pins
The MMIIC module uses two I/O pins, shared with standard port I/O pins. The full name of the MMIIC I/O
pins are listed in Table 14-1. The generic pin name appear in the text that follows.
The SDA and SDL pins are open-drain. When configured as general purpose output pins (PTB0 and
PTB1), pullup resistors must be connected to these pins.
Table 14-1. Pin Name Conventions
MMIIC Generic Pin Names:
SDA
SCL
Full MCU Pin Names:
PTB0/SDA
PTB1/SCL
Pin Selected for MMIIC Function By:
MMEN bit in MMCR1 ($0049)
Addr.
$0048
$0049
$004A
$004B
$004C
$004D
$004E
$004F
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
MMIIC Address Register
(MMADR)
Write:
MMAD7
Reset: 1
MMAD6
0
MMAD5
1
MMAD4
0
MMAD3
0
MMAD2
0
MMAD1 MMEXTAD
0
0
Read:
MMIIC Control Register 1
(MMCR1)
Write:
MMEN
MMIEN
0
MMCLRBB
0
Reset: 0
0
0
0
0
MMTXAK REPSEN MMCRCBYTE
0
0
0
0
Read: MMALIF MMNAKIF
MMIIC Control Register 2
(MMCR2)
Write:
0
0
MMBB
MMAST
MMRW
0
Reset: 0
0
0
0
0
0
0
MMCRCEF
0
Unaffected
Read: MMRXIF
MMIIC Status Register
(MMSR)
Write:
0
Reset: 0
MMTXIF
0
0
MMATCH MMSRW MMRXAK MMCRCBF MMTXBE MMRXBF
0
0
1
0
1
0
MMIIC Data Transmit ^Read: _{MMTD7 MMTD6 MMTD5 MMTD4 MMTD3 MMTD2 MMTD1 MMTD0}
Register Write:
(MMDTR) Reset: 0
0
0
0
0
0
0
0
MMIIC Data Receive ^{Read: MMRD7 MMRD6 MMRD5 MMRD4 MMRD3 MMRD2 MMRD1 MMRD0}
Register Write:
(MDDRR) Reset: 0
0
0
0
0
0
0
0
Read: MMCRCD7 MMCRCD6 MMCRCD5 MMCRCD4 MMCRCD3 MMCRCD2 MMCRCD1 MMCRCD0
MMIIC CRC Data Register
(MMCRDR)
Write:
Reset: 0
0
0
0
0
0
0
0
MMIIC Frequency Divider ^{Read: 0}
0
0
0
0
MMBR2 MMBR1 MMBR0
Register Write:
(MMFDR) Reset: 0
0
0
0
0
1
0
0
= Unimplemented
Figure 14-1. MMIIC I/O Register Summary
14.4 Multi-Master IIC System Configuration
The multi-master IIC system uses a serial data line SDA and a serial clock line SCL for data transfer. All
devices connected to it must have open collector (drain) outputs and the logical-AND function is
performed on both lines by two pull-up resistors.
MC68HC908AP Family Data Sheet, Rev. 4
230
Freescale Semiconductor