Datasheet

© 2009 Microchip Technology Inc. DS22153C-page 41
MCP9843/98243
5.3.4.2 Random Read
Random read operations allow the master to access
any memory location in a random manner. To perform
this type of read operation, the word address must first
be set. This is done by sending the word address to the
MCP98243 as part of a write operation. Once the word
address is sent, the master generates a start condition
following the acknowledge. This terminates the write
operation, but not before the internal address pointer is
set. The master then issues the Address Byte again,
but with the R/W
bit set to a ‘1’. The MCP98243 then
issues an acknowledge and transmits the 8-bit data
word. The master will not acknowledge the transfer but
does generate a stop condition and the MCP98243
discontinues transmission (Figure 5-19).
FIGURE 5-19: Timing Diagram for Random Read (See Section 4.0 “Serial Communication”).
SDA
A
C
K
1010
A
Word Address (n)
0000
A
C
K
S
2
A
1
A
0
12345678 12345678
SCL
0
Address Byte
MCP98243
MCP98243
W
000
1010
A
A
C
K
N
A
K
S P
2
A
1
A
0
12345678 12345678
Address Byte
Data at (n)
R
MCP98243
Master
SDA
SCL
XXXXX
XXX
Note: In this example, ‘n’ is the current Address Word which ‘00’h and the data is the byte at address ‘n’.