80C554 Datasheet, PDF (37/76 Pages) NXP Semiconductors – 80C51 8-bit microcontroller . 6 clock operation 16K/512 OTP/ROM/ROMless, 7 channel 10 bit A/D, I2C, PWM, capture/compare, high I/O, 64L LQFP

Philips Semiconductors
80C51 8-bit microcontroller – 6 clock operation
16K/512 OTP/ROM/ROMless, 7 channel 10 bit A/D, I²C, PWM,
capture/compare, high I/O, 64L LQFP
Preliminary specification
80C554/83C554/87C554
SDA
INTERNAL BUS
8
BSD7
S1DAT
ACK
SCL
SHIFT PULSES
SU00969
Figure 38. Serial Input/Output Configuration
SDA
D7
D6
D5
D4
D3
D2
D1
D0
A
SCL
SHIFT ACK & S1DAT
ACK
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
A
SHIFT IN
S1DAT
(1)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(1)
SHIFT BSD7
BSD7
D7
D6
D5
D4
D3
D2
D1
D0
(3)
SHIFT OUT
LOADED BY THE CPU
(1) Valid data in S1DAT
(2) Shifting data in S1DAT and ACK
(3) High level on SDA
Figure 39. Shift-in and Shift-out Timing
SU00970
In the following text, it is assumed that ENS1 = “1”.
STA, THE START FLAG
STA = “1”: When the STA bit is set to enter a master mode, the SIO1
hardware checks the status of the I2C bus and generates a START
condition if the bus is free. If the bus is not free, then SIO1 waits for
a STOP condition (which will free the bus) and generates a START
condition after a delay of a half clock period of the internal serial
clock generator.
If STA is set while SIO1 is already in a master mode and one or
more bytes are transmitted or received, SIO1 transmits a repeated
START condition. STA may be set at any time. STA may also be set
when SIO1 is an addressed slave.
STA = “0”: When the STA bit is reset, no START condition or
repeated START condition will be generated.
STO, THE STOP FLAG
STO = “1”: When the STO bit is set while SIO1 is in a master mode,
a STOP condition is transmitted to the I²C bus. When the STOP
condition is detected on the bus, the SIO1 hardware clears the STO
flag. In a slave mode, the STO flag may be set to recover from an
error condition. In this case, no STOP condition is transmitted to the
I²C bus. However, the SIO1 hardware behaves as if a STOP
condition has been received and switches to the defined “not
addressed” slave receiver mode. The STO flag is automatically
cleared by hardware.
2000 Nov 10
37