Motorola MC68VZ328 - Manual (Page 270)

14-18 MC68VZ328 User’s Manual
Programming Model
14.4.6 UART 1 Non-Integer Prescaler Register
The UART 1 non-integer prescaler register (NIPR1) contains the control bits for the non-integer prescaler.
The bit position assignments for this register are shown in the following register display. The settings for
this register are described in Table 14-9.
NIPR1 UART 1 Non-Integer Prescaler Register 0x(FF)FFF90A
BIT 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 BIT 0
PRE
SEL
SELECT STEP VALUE
TYPE rw rw rw rw rw rw rw rw rw rw rw rw
RESET
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0x0000
Table 14-9. UART 1 Non-Integer Prescaler Register Description
Name Description Setting
PRESEL
Bit 15 Prescaler Selection—This bit selects
the input to the baud rate generator
divider. Refer to Figure 14-4 on
page 14-7 for information about select-
ing the prescaler. 0 = Divider source is from the integer prescaler.
1 = Divider source is from the non-integer prescaler.
Reserved
Bits 14–11 Reserved These bits are reserved and should be set to 0.
SELECT
Bits 10–8 Tap Selection—This field selects a tap
from the non-integer divider. 000 = Divide range is 2 to 3 127/128 in 1/128 steps.
001 = Divide range is 4 to 7 63/64 in 1/64 steps.
010 = Divide range is 8 to 15 31/32 in 1/32 steps.
011 = Divide range is 16 to 31 15/16 in 1/16 steps.
100 = Divide range is 32 to 63 7/8 in 1/8 steps.
101 = Divide range is 64 to 127 3/4 in 1/4 steps.
110 = Divide range is 128 to 255 1/2 in 1/2 steps.
111 = Disable the non-integer prescaler.
STEP
VALUE
Bits 7–0 Step Value—This field selects the
non-integer prescaler’s step value. 0000 0000. Step = 0.
0000 0001. Step = 1.
.
.
.
1111 1110. Step = 254.
1111 1111. Step = 255.