VRS51C1000-40-QG-ISPV2 Ramtron, VRS51C1000-40-QG-ISPV2 Datasheet - Page 25

• Manufacturer Part Number: VRS51C1000-40-QG-ISPV2
• Description: Microcontrollers (MCU) 64K+1K 40MHz 5V
• Manufacturer: Ramtron

Specifications of VRS51C1000-40-QG-ISPV2

• Data Bus Width: 8 bit
• Program Memory Type: Flash
• Program Memory Size: 64 KB
• Data Ram Size: 1 KB
• Interface Type: UART
• Maximum Clock Frequency: 40 MHz
• Number Of Programmable I/os: 36
• Number Of Timers: 3
• Operating Supply Voltage: 4.5 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: QFP-44
• Minimum Operating Temperature: - 40 C
• Data Rom Size: 128 B
• Height: 2 mm
• Length: 10 mm
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 4.5 V
• Width: 10 mm
• Lead Free Status / Rohs Status: Details

UART Operation in Mode 3
In Mode 3, 11 bits are transmitted (through TXD) or
received
composed of: a Start bit (Low), 8 data bits (LSB first), a
programmable 9
Mode 3 is identical to Mode 2 in all respects but one:
the baud rate. Either Timer 1 or Timer 2 generates the
baud rate in Mode 3.
F
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SMOD
RCLK
IGURE
Timer 1
Overflow
VRS51C1000
÷2
0 1
Write to
19: S
0
0
SBUF
Timer 2
Overflow
1
1
RXD
TCLK
ERIAL
SAMPLE
1-0 Transition
Detector
(through
P
÷16
1
ORT
S
D
CLK
M
RX Clock
Start
Detector
th
LOAD SBUF
Start
TX Clock
÷16
ODE
Bit
Q
data bit, and one Stop bit (High).
3 B
Shift
ZERO DETECTOR
RXD).
LOCK
TX Control Unit
RX Control Unit
Internal Bus
D
TI
RI
Internal Bus
IAGRAM
SBUF
SBUF
9-Bit Shift Register
The
Serial Port
Interrupt
Shift
Send
Data
SHIFT
READ SBUF
SBUF
Load
transactions
are
TXD
UART in Mode 2 and 3: Additional Information
As mentioned previously, for an operation in Modes 2
and 3, 11 bits are transmitted (through TXD) or
received (through RXD). The signal comprises: a
logical low Start bit, 8 data bits (LSB first), a
programmable 9
bit.
On transmit, (TB8 in SCON) can be assigned the value
of 0 or 1. On receive; the 9
SCON. The baud rate is programmable to either 1/32
or 1/64 the oscillator frequency in Mode 2. Mode 3 may
have a variable baud rate generated from either Timer
1 or Timer 2 depending on the states of TCLK and
RCLK.
UART Transmission in Mode 2 and Mode 3
The transmission is initiated by any instruction that
makes use of SBUF as the destination register. The 9
bit position of the transmit shift register is loaded by the
“write to SBUF” signal. This event also informs the
UART transmission control unit that a transmission has
been requested. After the next rollover in the divide-by-
16 counter, a transmission actually starts at the
beginning of the machine cycle. It follows that the bit
times are synchronized to the divide-by-16 counter and
not to the “write to SBUF” signal, as in the previous
mode.
Transmissions begin when the SEND signal is
activated, which places the Start bit on TXD pin. Data
is activated one bit time later. This activation enables
the output bit of the transmit shift register to the TXD
pin. The first shift pulse occurs one bit time after that.
The first shift clocks a Stop bit (1) into the 9
position of the shift register on TXD. Thereafter, only
zeros are clocked in. Thus, as data bits shift out to the
right, zeros are clocked in from the left. When TB8 is at
the output position of the shift register, the stop bit is
just to the left of TB8, and all positions to the left of that
contain zeros. This condition signals to the TX control
unit to shift one more time and set TI, while
deactivating SEND. This occurs at the 11
16 rollover after “write to SBUF”.
th
data bit, and one logical high Stop
th
data bit goes into RB8 in
page 25 of 48
th
divide-by-
th
bit
th