參數(shù)資料
型號: 935263366112
廠商: NXP SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 16 MHz, MICROCONTROLLER, PQCC44
封裝: PLASTIC, LCC-44
文件頁數(shù): 29/80頁
文件大?。?/td> 446K
代理商: 935263366112
1997 Dec 15
35
Philips Semiconductors
Product specication
8-bit microcontrollers
P83C524; P80C528; P83C528
13.2.1
READING OR WRITING THE S1BIT SFR
Reading or writing the S1BIT SFR starts an I2C bit I/O
sequence: some flags are cleared (SI, CLH, RBF, WBF),
clock stretching is finished and the auto-clock is started.
An auto-clock pulse is 'OR-ed' with SCO and thus will be
output only if the SCO flag has been set to 0. SCO = 1
inhibits the auto-clock start, so a dummy read or write of
S1BIT SFR can be used to finish clock stretching and clear
SI, CLH, RBF and WBF if the auto-clock is not used.
The auto-clock is an active HIGH SCL pulse that starts 28
XTAL clock periods after the SDI read or SDO write via
S1BIT. The duration of the auto-clock pulse is 100 XTAL
clock periods. If the SCL line is kept LOW by any device
that wants to hold up the bus transfer, the auto-clock
counter waits after 20 XTAL clock periods so that the
auto-clock pulse length will be at least 80 XTAL clock
periods (5
s at fOSC = 16 MHz).
Every bit I/O should be followed by a RBF or WBF bit test.
A bit transfer has been finished successfully if after reading
a bit the RBF flag is 1 or after writing a bit the WBF flag is
1. When after reading a bit the RBF flag is still 0, the bus
status just before the S1SCS status read can be
determined as follows:
if CLH = 0 then a bus device is still stretching the clock
if SCI = 1 while CLH = 1 then the SCL pulse is not
finished
if BB = 0 there has been a STOP condition.
When after writing a bit the WBF flag is still 0 and none of
the 3 status conditions mentioned for RBF are found then
a 'bus arbitration lost' condition will be the cause. This can
be determined also from the states of the received bit and
the last transmitted bit: 'arbitration loss' if SDO = 1 and
SDI = 0.
13.3
Control and Status Register for the I2C-bus (S1SCS)
Table 19 Control and Status register for the I2C-bus (address D8H)
Notes
1. SDI and SCI bits: read-modify-write operations like 'SETB bit' or 'CLR bit' access SDO and SCO for reading and
writing.
2. CLH bit: writing a logic 0 clears this bit, writing a 1 has no effect.
3. RBF and WBF bits: writing a logic 0 to CLH also clears these bits.
4. X = don't care.
76543210
READ
SDI(1)
SCI(1)
CLH(2)
BB
RBF(3)
WBF(4)
STR
ENS
WRITE
SDO
SCO
CLH(2)
X
STR
ENS
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