SCS152

© 1997 Microchip Technology Inc.

Preliminary

DS40150B-page 3

2.4

Digit Fields

2.4.1

DIGIT FIELD VALUE

Each digit field, D4 to D0, represents a number equal to

the number of ‘1’ bits in the field. Table 2-2 shows the

value of the digit field for each legal digit value.

TABLE 2-2:

DIGIT FIELD VALUES

2.4.2

TOKEN COUNTER VALUE

The following formula shows how the digit fields combine to form the token counter value:

This is, in fact, an octal representation of a value and can be written as:

Suppose the 5-digit field contain the values: (D4=3), (D3=0), (D2=7), (D1=1), (D0=3). The token counter value is then

A digit needs to be set to eight to handle the borrow from the next higher stage. This also implies that each counter value

Digit Value

Field Value

0

0000 0000

1

1000 0000

2

1100 0000

3

1110 0000

4

1111 0000

5

1111 1000

6

1111 1100

7

1111 1110

8

1111 1111

Note:

The bits are shown, right to left, in the order

in which they are read out.

Note:

The value digit D4 is shown in the formulas as |D4| indicating the number of 1 bits in the digit D4 field.

Similarly |D3| indicates the number of 1 bits in the digit D3 field, and so on.

Tokens

D4

4096

D3

512

D2

64

D1

8

D0

+

×

+

×

+

×

+

×

=

Tokens

D4

8

4

D3

8

3

D2

8

2

D1

8

1

D0

8

0

×

+

×

+

×

+

×

+

×

=

Tokens

3

4096

0

512

7

64

1

8

3

+

×

+

×

+

×

+

×

12747

10

=

=