at89lp2052-20xi ATMEL Corporation, at89lp2052-20xi Datasheet - Page 42

• Manufacturer Part Number: at89lp2052-20xi
• Description: At89lp2052 8-bit Microcontroller With 2/4-kbyte Flash
• Manufacturer: ATMEL Corporation

42
AT89LP2052/LP4052
The interconnection between master and slave CPUs with SPI is shown in
pins in the interface are Master-In/Slave-Out (MISO), Master-Out/Slave-In (MOSI), Shift Clock
(SCK), and Slave Select (SS). The SCK pin is the clock output in master mode, but is the clock
input in slave mode. The MSTR bit in SPCR determines the directions of MISO and MOSI. Also
notice that MOSI connects to MOSI and MISO to MISO. In master mode, SS/P1.4 is ignored and
may be used as a general-purpose input or output. In slave mode, SS must be driven low to
select an individual device as a slave. When SS is driven high, the slave’s SPI port is deacti-
vated and the MOSI/P1.5 pin can be used as a general-purpose input.
Figure 19-1. SPI Master-Slave Interconnection
Figure 19-2. SPI Block Diagram
Clock Generator
÷4÷8÷32÷64
SPI
SPI Status Register
Oscillator
Select
Divider
MSB
SPI Control
8-Bit Shift Register
SPI Clock (Mater)
Master
SPI Interrupt
Request
MSTR
SPE
8
LSB
MSB
Data Bus
Internal
8
8-bit Shift Register
Read Data Buffer
Write Data Buffer
8
MISO
MOSI MOSI
SCK
SS
V
CC
SPI Control Register
MISO
SCK
SS
Clock
Logic
LSB
Clock
MSB
8-Bit Shift Register
S
M
M
S
S
M
Slave
Figure
3547H–MICRO–5/07
MISO
MOSI
19-1. The four
P1.6
P1.5
SCK
P1.4
1.7
SS
LSB