Motorola MC68VZ328 14.4.9 UART 2 Baud Control Register

14-22 MC68VZ328 User’s Manual 
Programming Model
14.4.9 UART 2 Baud Control Register
The UART 2 baud control (UBAUD2) register controls the operation of the baud rate generator, the
integer prescaler, and the UCLK signal. The bit position assignments for this register are shown in the
following register display. The settings for this register are described in Table 14-11.
UBAUD2 UART 2 Baud Control Register 0x(FF)FFF912
BIT 151413 12 11 10987654321BIT 0
UCLK
DIR BAUD SRC DIVIDE PRESCALER
TYPE rw rw rw rw rw rw rw rw rw rw rw
RESET 0 0 0 0 0 0000011111 1
0x003F
Table 14-11. UART 2 Baud Control Register Description
Name Description Setting
Reserved
Bits 15–14 Reserved These bits are reserved and should be set to 0.
UCLKDIR
Bit 13 UCLK Direction—This bit controls the direction of the UCLK signal. When this bit
is low, the signal is an input, and when it is
high, it is an output. However, the SELx bit
in the Port E registers must be 0. See
Section10.4.6, “Port E Registers,” on
page10-21 for more information.
0 = UCLK is an input.
1 = UCLK is an output.
Reserved
Bit 12 Reserved This bit is reserved and should be set to 0.
BAUD SRC
Bit 11 Baud Source—This bit controls the clock source to the baud rate generator. 0 = Baud rate generator source is from system clock.
1 = Baud rate generator source is from UCLK pin
(UCLKDIR must be set to 0).
DIVIDE
Bits 10–8 Divide—These bits control the clock fre- quency produced by the baud rate genera-
tor.
000 = Divide by 1.
001 = Divide by 2.
010 = Divide by 4.
011 = Divide by 8.
100 = Divide by 16.
101 = Divide by 32.
110 = Divide by 64.
111 = Divide by 128.
Reserved
Bits 7–6 Reserved These bits are reserved and should be set to 0.
PRESCALER
Bits 5–0 Prescaler—These bits control the division value of the baud generator prescaler. The
division value is determined by the follow-
ing formula:
Prescaler division value =
65 (decimal) – PRESCALER
See description.