Microchip Technology TSSOP20EV Data Sheet
© 2009 Microchip Technology Inc.
DS22233A-page 47
MCP434X/436X
7.0
DEVICE COMMANDS
The MCP43XX’s SPI command format supports 16
memory address locations and four commands. Each
command has two modes. These are:
memory address locations and four commands. Each
command has two modes. These are:
• Normal Serial Commands
• High-Voltage Serial Commands
• High-Voltage Serial Commands
Normal serial commands are those where the CS pin is
driven to V
driven to V
IL
. With High-Voltage Serial Commands, the
CS pin is driven to V
IHH
. In each mode, there are four
possible commands. These commands are shown in
The 8-bit commands (
and
commands) contain a Command
Byte, see
, while 16-bit commands (
and
commands) contain a Command
Byte and a Data Byte. The Command Byte contains
two data bits, see
two data bits, see
.
shows the supported commands for each
memory location and the corresponding values on the
SDI and SDO pins.
SDI and SDO pins.
shows an overview of all the SPI commands
and their interaction with other device features.
7.1
Command Byte
The Command Byte has three fields, the Address, the
Command, and 2 Data bits, see
Command, and 2 Data bits, see
only one of the data bits is defined (D8). This is for the
Write command.
Write command.
The device memory is accessed when the master
sends a proper Command Byte to select the desired
operation. The memory location getting accessed is
contained in the Command Byte’s AD3:AD0 bits. The
action desired is contained in the Command Byte’s
C1:C0 bits, see
sends a proper Command Byte to select the desired
operation. The memory location getting accessed is
contained in the Command Byte’s AD3:AD0 bits. The
action desired is contained in the Command Byte’s
C1:C0 bits, see
. C1:C0 determines if the
desired memory location will be read, written,
Incremented (wiper setting +1) or Decremented (wiper
setting -1). The Increment and Decrement commands
are only valid on the volatile wiper registers, and in
High Voltage commands to enable/disable WiperLock
Technology and Software Write Protect.
Incremented (wiper setting +1) or Decremented (wiper
setting -1). The Increment and Decrement commands
are only valid on the volatile wiper registers, and in
High Voltage commands to enable/disable WiperLock
Technology and Software Write Protect.
As the Command Byte is being loaded into the device
(on the SDI pin), the device’s SDO pin is driving. The
SDO pin will output high bits for the first six bits of that
command. On the 7th bit, the SDO pin will output the
CMDERR bit state (see Section 7.3 “Error
Condition”). The 8th bit state depends on the
command selected.
(on the SDI pin), the device’s SDO pin is driving. The
SDO pin will output high bits for the first six bits of that
command. On the 7th bit, the SDO pin will output the
CMDERR bit state (see Section 7.3 “Error
Condition”). The 8th bit state depends on the
command selected.
TABLE 7-1:
COMMAND BIT OVERVIEW
FIGURE 7-1:
General SPI Command Formats.
C1:C0
Bit
States
Command
# of
Bits
Operates on
Volatile/
Non-Volatile
memory
Volatile/
Non-Volatile
memory
11
Read Data
16-Bits
Both
00
Write Data
16-Bits
Both
01
Increment
8-Bits
Volatile
Only
10
Decrement
8-Bits
Volatile
Only
Note 1: High Voltage Increment and Decrement
commands on select non-volatile memory
locations enable/disable WiperLock
Technology and the software Write
Protect feature.
locations enable/disable WiperLock
Technology and the software Write
Protect feature.
A
D
D
3
A
D
D
2
A
D
D
1
A
D
D
0
C
1
C
0
D
9
D
8
Memory
Command Byte
Data
Address
Bits
Command
Bits
A
D
D
3
A
D
2
A
D
1
A
D
0
C
1
C
0
D
9
D
8
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
Memory
16-bit Command
Data
Address
Bits
Command
Bits
0 0 = Write Data
0 1 = INCR
0 1 = INCR
1 0 = DECR
1 1 = Read Data
1 1 = Read Data
C C
1 0
1 0
Command
Bits
8-bit Command
Command Byte
Data Byte