z16f2811 ZiLOG Semiconductor, z16f2811 Datasheet - Page 312

• Manufacturer Part Number: z16f2811
• Description: High Performance Microcontrollers
• Manufacturer: ZiLOG Semiconductor

Table 165. OCD Baud Rate Limits
PS022006-0207
System Clock
Frequency
20.0 MHz
1.0 MHz
Baud Rate Generator
bit is high, the data was correctly framed between a start and stop bit. After the receiver
samples the middle of the stop bit, it begins searching for another start bit. The receiver
does not wait for the full stop bit to be received before searching for the next start bit.
This is to correct for any bit skew due to error between the transmit and receive baud rate
clocks.
The baud rate generator (BRG) is used to generate a bit clock for transmit and receive
operations. The BRG reload register is automatically configured by the auto-baud
detector, or it is written by software.
The value in the BRG reload register is calculated as:
This reload value is the number of system clocks used to transmit and receive eight data
bits.
The BRG has a 16-bit reload counter and is clocked by the system clock. When the OCD
is enabled, this register is limited to 12 bits. The minimum baud rate is calculated using the
following equation:
The minimum baud rate when the OCD is enabled is the system clock frequency divided
by 512. The minimum baud rate is the system clock frequency divided by 8192 when the
OCD is disabled.
For asynchronous operation, the maximum baud rate is roughly the system clock
frequency divided by eight (eight clocks per bit). With slow baud rates and clean signals,
you will be able to achieve asynchronous baud rates up to 4 clocks per bit. If data is
synchronized with the system clock, the maximum baud rate is the system clock frequency
(one bit per clock). The maximum baud rates are limited by the rise and fall times due to
the cable impedance.
crystal frequencies.
BAUD RELOAD VALUE =
BAUD RELOAD VALUE =
2.5 M baud
Baud Rate
125 k baud
Maximum
Table 165
P R E L I M I N A R Y
*
lists minimum and maximum baud rates for sample
Minimum Baud Rate
SYSTEM CLOCK
SYSTEM CLOCK
BAUD RATE
BAUD RATE
(OCDEN=0)
2442 baud
123 baud
x 8
x 8
Product Specification
Minimum Baud Rate
ZNEO
39,062 baud
(OCDEN=1)
On-Chip Debugger
1953 baud
™
Z16F Series
298