
Communication Processor Module
16-388
MPC823 USER’S MANUAL
MOTOROLA
SMC
COMMUNICATION
16
PROCESSOR
MODULE
16.11.6.10 SMC UART MODE REGISTER. When the SMC is in UART mode, the 16-bit,
memory-mapped, read/write SMC mode register is referred to as the SMC UART mode
register (SMCMR–UART). The functionality of bits 8-15 is common to each SMC protocol,
but bits 0-7 vary according to the protocol selected by the SM field. This register is cleared
by reset.
Bits 0 and 8–9—Reserved
These bits are reserved and should be set to 0.
CLEN—Character Length
This field should be programmed with the total number of bits in the character minus one.
The total number of bits in the character is calculated as the sum of 1 (start bit always
present) + number of data bits (5 to 14) + number of parity bits (0 or 1) + number of stop bits
(1 or 2). For example, for 8 data bits, no parity, and 1 stop bit, the total number of bits in the
character is 1 + 8 + 0 + 1 = 10. So, CLEN should be programmed to 9.
The number of data bits in the character ranges from 5 to 14 bits. If the data bit length is less
than 8 bits, the most-significant bits of each byte in memory are not used on transmission
and are written with zeros on reception. On the other hand, if the data bit length is more than
8 bits, the most-significant bits of each 16-bit word in memory are not used on transmit and
are written with zeros on receive.
SL—Stop Length
0 = One stop bit.
1 = Two stop bits.
PEN—Parity Enable
0 = No parity.
1 = Parity is enabled for the transmitter and receiver as determined by the PM bit.
SMCMR–UART
BIT
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
FIELD
RES
CLEN
SL
PEN
PM
RES
SM
DM
TEN
REN
RESET
0
000
0
00
R/W
R/W
ADDR
(IMMR & 0xFFFF0000) + 0xA82 (SMC1), 0xA92 (SMC2)
Note: The total number of bits in the character must never exceed 16. Thus, if you
choose a 14-bit data length, you should set SL to one stop bit and not enable
parity. If you choose a 13-bit data length and parity is enabled, you should set
SL to one stop bit. You should not write the values 0-3 to CLEN or else erratic
behavior will occur.