MCP433X datasheet(59/88 Pages) MICROCHIP

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DS22242A-page 59

MCP433X/435X

7.7

Increment Wiper

Normal and High Voltage

The Increment command is an 8-bit command. The

Increment command can only be issued to volatile

memory locations. The format of the command is

shown in Figure 7-6.

An Increment command to the volatile memory location

changes that location after a properly formatted com-

mand (8-clocks) have been received.

Increment commands provide a quick and easy

method to modify the value of the volatile wiper location

by +1 with minimal overhead.

FIGURE 7-6:

Increment Command –

SDI and SDO States.

7.7.1

SINGLE INCREMENT

Typically, the CS pin starts at the inactive state (VIH),

but may already be in the active state due to the

completion of another command.

Figure 6-4

through

Figure 6-5

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 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

Increment command is disabled. See Table 7-4 for

additional information on the Increment command

versus the current volatile wiper value.

The increment operations only require the Increment

command byte while the CS pin is active (VILor VIHH)

for a single increment.

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.

Note:

Table 7-2 shows the valid addresses for

the Increment Wiper command. Other

addresses are invalid.

111111 1* 1 Note 1, 2

111111

0 Note 1, 3

(INCR COMMAND (n+1))

SDI

SDO

COMMAND BYTE

Note 1: Only functions when writing the volatile

wiper registers (AD3:AD0) 0h and 1h.

2: Valid Address/Command combination.

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).

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).

TABLE 7-4:

INCREMENT OPERATION VS.

VOLATILE WIPER VALUE

Current Wiper

Setting

Wiper (W)

Properties

Increment

Command

Operates?

7-bit

Pot

8-bit

Pot

3FFh

081h

3FFh

101h

Reserved

(Full Scale (W = A))

080h

100h

Full Scale (W = A)

07Fh

041h

0FFh

081

W = N

040h

080h

W = N (Mid-scale)

Yes

03Fh

001h

07Fh

001

W = N

000h

Zero Scale (W = B)

Yes

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