MCP413X/415X/423X/425X
7.7.1
SINGLE INCREMENT
7.7
Increment Wiper
Normal and High Voltage
Typically, the CS pin starts at the inactive state (VIH),
but may be already be in the active state due to the
completion of another command.
Note:
The High Voltage Increment Wiper
command is supported for compatability
with system that also support MCP414X/
416X/424X/426X devices.
Figure 6-7 through Figure 6-8 show possible
waveforms for a single increment. The increment
operation requires that the CS pin be in the active state
(VILor VIHH). Typically, the CS pin will be in the inactive
state (VIH) and is driven to the active state (VILor VIHH).
The 8-bit Increment Command (Command Byte) is
then clocked in on the SDI pin by the SCK pins. The
SDO pin drives the CMDERR bit on the 7th clock.
The Increment Command is an 8-bit command. The
Increment Command can only be issued to wiper
memory locations. The format of the command is
shown in Figure 7-6.
An Increment Command to the wiper memory location
changes that location after a properly formatted
command (8-clocks) have been received.
The wiper value will increment up to 100h on 8-bit
devices and 80h on 7-bit devices. After the wiper value
has reached Full-Scale (8-bit =100h, 7-bit =80h), the
wiper value will not be incremented further. If the Wiper
register has a value between 101h and 1FFh, the
Increment command is disabled. See Table 7-4 for
additional information on the Increment Command
versus the current volatile wiper value.
Increment commands provide a quick and easy
method to modify the value of the wiper location by +1
with minimal overhead.
COMMAND BYTE
(INCR COMMAND (n+1) )
The Increment operations only require the Increment
command byte while the CS pin is active (VILor VIHH
for a single increment.
)
A
D
3
A
D
2
A
D
1
A
D
0
0
1
X
X
SDI
After the wiper is incremented to the desired position,
the CS pin should be forced to VIH to ensure that
unexpected transitions on the SCK pin do not cause
the wiper setting to change. Driving the CS pin to VIH
should occur as soon as possible (within device
specifications) after the last desired increment occurs.
1
1
1
1
1
1
1
1
1
1
1
1
1*
0
1
0
Note 1, 2
Note 1, 3
SDO
Note 1: Only functions when writing the volatile
wiper registers (AD3:AD0) 0h and 1h.
2: Valid Address/Command combination.
TABLE 7-4:
INCREMENT OPERATION VS.
VOLATILE WIPER VALUE
3: Invalid Address/Command combination
all following SDO bits will be low until the
CMDERR condition is cleared.
(the CS pin is forced to the inactive
state).
Current Wiper
Setting
Increment
Wiper (W)
Command
Operates?
Properties
7-bit
Pot
8-bit
Pot
4: If a Command Error (CMDERR) occurs
at this bit location (*), then all following
SDO bits will be driven low until the CS
pin is driven inactive (VIH).
3FFh
081h
3FFh Reserved
101h (Full-Scale (W = A))
No
No
080h
100h Full-Scale (W = A)
07Fh
041h
0FFh W = N
081
FIGURE 7-6:
SDI and SDO States.
Increment Command -
040h
080h W = N (Mid-Scale)
Yes
Yes
03Fh
001h
07Fh W = N
001
000h
000h Zero Scale (W = B)
© 2008 Microchip Technology Inc.
DS22060B-page 55
MICROCHIP [ MICROCHIP ]
