PIC17C75X Datasheet, PDF (107/320 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers

14.0 UNIVERSAL SYNCHRONOUS
ASYNCHRONOUS RECEIVER
TRANSMITTER (USART)
MODULES
Each USART module is a serial I/O module. There are
two USART modules that are available on the
PIC17C75X. They are specified as USART1 and
USART2. The description of the operation of these
modules is generic in regard to the register names and
pin names used. Table 14-1 shows the generic names
that are used in the description of operation and the
actual names for both USART1 and USART2. Since
the control bits in each register have the same function,
their names are the same (there is no need to differen-
tiate).
The Transmit Status And Control Register (TXSTA) is
shown in Figure 14-1, while the Receive Status And
Control Register (RCSTA) is shown in Figure 14-2.
PIC17C75X
TABLE 14-1: USART MODULE GENERIC
NAMES
Generic name USART1 name USART2 name
Registers
RCSTA
RCSTA1
RCSTA2
TXSTA
TXSTA1
TXSTA2
SPBRG
SPBRG1
SPBRG2
RCREG
RCREG1
RCREG2
TXREG
TXREG1
TXREG2
Interrupt Control Bits
RCIE
RC1IE
RC2IE
RCIF
RC1IF
RC2IF
TXIE
TX1IE
TX2IE
TXIF
TX1IF
TX2IF
Pins
RX/DT
RA4/RX1/DT1 RG6/RX2/DT2
TX/CK
RA5/TX1/CK1 RG7/TX2/CK2
FIGURE 14-1: TXSTA1 REGISTER (ADDRESS: 15h, BANK 0)
TXSTA2 REGISTER (ADDRESS: 15h, BANK 4)
R/W - 0 R/W - 0 R/W - 0 R/W - 0
CSRC TX9 TXEN SYNC
bit7
U-0
—
U-0
—
R-1
TRMT
bit 7:
CSRC: Clock Source Select bit
Synchronous mode:
1 = Master Mode (Clock generated internally from BRG)
0 = Slave mode (Clock from external source)
Asynchronous mode:
Don’t care
R/W - x
TX9D
bit0
R = Readable bit
W = Writable bit
-n = Value at POR reset
(x = unknown)
bit 6:
TX9: 9-bit Transmit Select bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission
bit 5:
TXEN: Transmit Enable bit
1 = Transmit enabled
0 = Transmit disabled
SREN/CREN overrides TXEN in SYNC mode
bit 4:
SYNC: USART Mode Select bit
(Synchronous/Asynchronous)
1 = Synchronous mode
0 = Asynchronous mode
bit 3-2: Unimplemented: Read as '0'
bit 1:
TRMT: Transmit Shift Register (TSR) Empty bit
1 = TSR empty
0 = TSR full
bit 0: TX9D: 9th bit of transmit data (can be used to calculated the parity in software)
© 1997 Microchip Technology Inc.
Preliminary
DS30264A-page 107