ADUC812 Analog Devices, ADUC812 Datasheet - Page 27

• Manufacturer Part Number: ADUC812
• Description: Precision Analog Microcontroller: 1.3MIPS 8052 MCU + 8kB Flash + 8-Ch 12-Bit ADC + Dual 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC812

• Mcu Core: 8052
• Mcu Speed (mips): 1.3
• Sram (bytes): 256Bytes
• Gpio Pins: 34
• Adc # Channels: 8

SPIDAT
Function
SFR Address
Power-On Default Value
Bit Addressable
Using the SPI Interface
Depending on the configuration of the bits in the SPICON SFR
shown in Table XI, the ADuC812 SPI interface will transmit or
receive data in a number of possible modes. Figure 25 shows all
possible ADuC812 SPI configurations and the timing relationships
and synchronization between the signals involved. Also shown in
this figure is the SPI interrupt bit (ISPI) and how it is triggered
at the end of each byte wide communication.
REV. E
SAMPLE INPUT
SAMPLE INPUT
DATA OUTPUT
DATA OUTPUT
(CPOL = 1)
(CPOL = 0)
ISPI FLAG
ISPI FLAG
SCLOCK
SCLOCK
SS
Figure 25. SPI Timing, All Modes
?
MSB
MSB
BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB ?
SPI Data Register
The SPIDAT SFR is written by the
user to transmit data over the SPI
interface or read by user code to read
data just received by the SPI interface.
F7H
00H
No
BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB
–27–
SPI Interface—Master Mode
In master mode, the SCLOCK pin is always an output and gener-
ates a burst of eight clocks whenever user code writes to the
SPIDAT register. The SCLOCK bit rate is determined by SPR0
and SPR1 in SPICON. It should also be noted that the SS pin
is not used in master mode. If the ADuC812 needs to assert the
SS pin on an external slave device, a Port digital output pin
should be used.
In master mode a byte transmission or reception is initiated by
a write to SPIDAT. Eight clock periods are generated via the
SCLOCK pin and the SPIDAT byte being transmitted via MOSI.
With each SCLOCK period a data bit is also sampled via
MISO. After eight clocks, the transmitted byte will have been
completely transmitted and the input byte will be waiting in
the input shift register. The ISPI flag will be set automatically
and an interrupt will occur if enabled. The value in the shift
register will be latched into SPIDAT.
SPI Interface—Slave Mode
In slave mode the SCLOCK is an input. The SS pin must also
be driven low externally during the byte communication.
Transmission is also initiated by a write to SPIDAT. In slave mode,
a data bit is transmitted via MISO and a data bit is received via
MOSI through each input SCLOCK period. After eight clocks,
the transmitted byte will have been completely transmitted and
the input byte will be waiting in the input shift register. The
ISPI flag will be set automatically and an interrupt will occur
if enabled. The value in the shift register will be latched into
SPIDAT only when the transmission/reception of a byte has been
completed. The end of transmission occurs after the eighth
clock has been received if CPHA = 1, or when SS returns high
if CPHA = 0.
ADuC812