Signal
Name
Alternate
Function
Type Description
Analog Power Supply 2
AVDD2
AVSS2
PWR
-
-
Low Voltage system: connect this pin to LVDD pin.
High voltage system: connect this pin to external +3V power supply.
Analog Ground 2
GND
Low Voltage system: connect this pin to LVSS pin.
High voltage system: connect this pin to external +3V ground.
Parallel Slave Interface
Table 10. PSI Signal Description
Signal
Name
Alternate
Function
Type Description
Slave Data Bus
P0.7:0
LD7:0
SD7:0
I/O
8-bit bidirectional data bus.
Slave Read Signal
P5.0
SRD
SWR
SCS
SA0
I
I
I
I
Read signal asserted low during external host read operation.
LRD/LDE
Slave Write Signal
P5.3
Write signal asserted low during external host write operation.
LWR/LRW
Slave Chip Select
P5.1
LCS
Select signal asserted low during external host read or write operation.
Slave Address Bit 0
P5.2
Address signal asserted during external host read or write operation.
LA0/LRS
Serial Interfaces
Table 11. SPI Controller Signal Description
Signal
Name
Alternate
Function
Type Description
SPI Master Input Slave Output Data Line
P3.0
RXD
MISO
I/O
I/O
I/O
When in master mode, MISO receives data from the slave peripheral.
When in slave mode, MISO outputs data to the master controller.
SPI Master Output Slave Input Data Line
P3.1
TXD
MOSI
SCK
SS
When in master mode, MOSI outputs data to the slave peripheral.
When in slave mode, MOSI receives data from the master controller.
P3.2
INT0
RTS
SPI Clock Line
When in master mode, SCK outputs clock to the slave peripheral.
When in slave mode, SCK receives clock from the master controller.
P3.3
INT1
CTS
SPI Slave Select Line
I
When in controlled slave mode, SS enables the slave mode.
Table 12. SIO Signal Description
Signal
Name
Alternate
Function
Type Description
Receive Serial Data
I/O RXD sends and receives data in serial I/O mode 0 and receives data in
serial I/O modes 1, 2 and 3.
P3.0
RXD
MISO
12
AT85C51SND3Bx
7632A–MP3–03/06
ATMEL [ ATMEL ]
