PIC16F628-20I/P Microchip Technology, PIC16F628-20I/P Datasheet - Page 83

• Manufacturer Part Number: PIC16F628-20I/P
• Description: IC MCU FLASH 2KX14 COMP 18DIP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F628-20I/P

• Program Memory Type: FLASH
• Program Memory Size: 3.5KB (2K x 14)
• Package / Case: 18-DIP (0.300", 7.62mm)
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 16
• Eeprom Size: 128 x 8
• Ram Size: 224 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 224 B
• Interface Type: SCI/USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 16
• Number Of Timers: 3
• Operating Supply Voltage: 3 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, DM163014, DM164120-4
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: DVA16XP183 - ADAPTER ICE 18DIP/SOIC/SSOPAC164010 - MODULE SKT PROMATEII DIP/SOIC
• Data Converters: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

12.4
In Synchronous Master mode, the data is transmitted in
a half-duplex manner (i.e., transmission and reception
do not occur at the same time). When transmitting data,
the reception is inhibited and vice versa. Synchronous
mode is entered by setting bit SYNC (TXSTA<4>). In
addition, enable bit SPEN (RCSTA<7>) is set in order
to configure the RB2/TX/CK and RB1/RX/DT I/O pins
to CK (clock) and DT (data) lines respectively. The
Master mode indicates that the processor transmits the
master clock on the CK line. The Master mode is
entered by setting bit CSRC (TXSTA<7>).
12.4.1
The USART Transmitter Block Diagram is shown in
Figure 12-5. The heart of the transmitter is the Transmit
(serial) Shift register (TSR). The Shift register obtains
its data from the read/write transmit buffer register
TXREG. The TXREG register is loaded with data in
software. The TSR register is not loaded until the last
bit has been transmitted from the previous load. As
soon as the last bit is transmitted, the TSR is loaded
with new data from the TXREG (if available). Once the
TXREG register transfers the data to the TSR register
(occurs in one Tcycle), the TXREG is empty and
interrupt bit, TXIF (PIR1<4>) is set. The interrupt can
be enabled/disabled by setting/clearing enable bit TXIE
(PIE1<4>). Flag bit TXIF will be set regardless of the
state of enable bit TXIE and cannot be cleared in soft-
ware. It will RESET only when new data is loaded into
the TXREG register. While flag bit TXIF indicates the
status of the TXREG register, another bit TRMT
(TXSTA<1>) shows the status of the TSR register.
TRMT is a read only bit which is set when the TSR is
empty. No interrupt logic is tied to this bit, so the user
has to poll this bit in order to determine if the TSR reg-
ister is empty. The TSR is not mapped in data memory
so it is not available to the user.
Transmission is enabled by setting enable bit TXEN
(TXSTA<5>). The actual transmission will not occur
until the TXREG register has been loaded with data.
The first data bit will be shifted out on the next available
rising edge of the clock on the CK line. Data out is sta-
ble around the falling edge of the synchronous clock
(Figure 12-12). The transmission can also be started
by first loading the TXREG register and then setting bit
TXEN (Figure 12-13). This is advantageous when slow
baud rates are selected, since the BRG is kept in
RESET when bits TXEN, CREN, and SREN are clear.
Setting enable bit TXEN will start the BRG, creating a
shift clock immediately. Normally when transmission is
first started, the TSR register is empty, so a transfer to
the TXREG register will result in an immediate transfer
to TSR resulting in an empty TXREG. Back-to-back
transfers are possible.
 2003 Microchip Technology Inc.
USART Synchronous Master
Mode
USART SYNCHRONOUS MASTER
TRANSMISSION
Preliminary
Clearing enable bit TXEN, during a transmission, will
cause the transmission to be aborted and will RESET
the transmitter. The DT and CK pins will revert to hi-
impedance. If either bit CREN or bit SREN is set,
during a transmission, the transmission is aborted and
the DT pin reverts to a hi-impedance state (for a recep-
tion). The CK pin will remain an output if bit CSRC is set
(internal clock). The transmitter logic however is not
RESET although it is disconnected from the pins. In
order to RESET the transmitter, the user has to clear bit
TXEN. If bit SREN is set (to interrupt an on-going
transmission and receive a single word), then after the
single word is received, bit SREN will be cleared and
the serial port will revert back to transmitting since bit
TXEN is still set. The DT line will immediately switch
from Hi-impedance Receive mode to transmit and start
driving. To avoid this, bit TXEN should be cleared.
In order to select 9-bit transmission, the TX9
(TXSTA<6>) bit should be set and the ninth bit should
be written to bit TX9D (TXSTA<0>). The ninth bit must
be written before writing the 8-bit data to the TXREG
register. This is because a data write to the TXREG can
result in an immediate transfer of the data to the TSR
register (if the TSR is empty). If the TSR was empty and
the TXREG was written before writing the “new” TX9D,
the “present” value of bit TX9D is loaded.
Steps to follow when setting up a Synchronous Master
Transmission:
1.
2.
3.
4.
5.
6.
7.
Initialize the SPBRG register for the appropriate
baud rate (Section 12.1).
Enable the synchronous master serial port by
setting bits SYNC, SPEN, and CSRC.
If interrupts are desired, then set enable bit
TXIE.
If 9-bit transmission is desired, then set bit TX9.
Enable the transmission by setting bit TXEN.
If 9-bit transmission is selected, the ninth bit
should be loaded in bit TX9D.
Start transmission by loading data to the TXREG
register.
PIC16F62X
DS40300C-page 81