ST72124J2 STMicroelectronics, ST72124J2 Datasheet - Page 95

• Manufacturer Part Number: ST72124J2
• Description: 8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY,ADC, 16-BIT TIMERS, SPI, SCI INTERFACES
• Manufacturer: STMicroelectronics

Specifications of ST72124J2

• Clock Sources: crystal/ceramic resonator oscillators or RC oscillators, external clock, backup Clock Security System
• 4 Power Saving Modes: Halt, Active-Halt, Wait and Slow
• Two 16-bit Timers With: 2 input captures (only one on timer A), 2 output compares (only one on timer A), External clock input on timer A, PWM and Pulse generator modes

SERIAL COMMUNICATIONS INTERFACE (Cont’d)
DATA REGISTER (DR)
Read/Write
Reset Value: Undefined
Contains the Received or Transmitted data char-
acter, depending on whether it is read from or writ-
ten to.
The Data register performs a double function (read
and write) since it is composed of two registers,
one for transmission (TDR) and one for reception
(RDR).
The TDR register provides the parallel interface
between the internal bus and the output shift reg-
ister (see Figure 1.).
The RDR register provides the parallel interface
between the input shift register and the internal
bus (see Figure 1.).
BAUD RATE REGISTER (BRR)
Read/Write
Reset Value: 00xx xxxx (XXh)
Bit 7:6= SCP[1:0] First SCI Prescaler
These 2 prescaling bits allow several standard
clock division ranges:
SCP1
DR7
7
7
PR Prescaling factor
SCP0
DR6
13
SCT2
1
3
4
DR5
SCT1
DR4
SCT0
DR3
SCP1
SCR2 SCR1 SCR0
DR2
0
0
1
1
DR1
SCP0
0
1
0
1
DR0
0
0
Bit 5:3 = SCT[2:0] SCI Transmitter rate divisor
These 3 bits, in conjunction with the SCP1 & SCP0
bits define the total division applied to the bus
clock to yield the transmit rate clock in convention-
al Baud Rate Generator mode.
Note: this TR factor is used only when the ETPR
fine tuning factor is equal to 00h; otherwise, TR is
replaced by the ETPR dividing factor.
Bit 2:0 = SCR[2:0] SCI Receiver rate divisor.
These 3 bits, in conjunction with the SCP1 & SCP0
bits define the total division applied to the bus
clock to yield the receive rate clock in conventional
Baud Rate Generator mode.
Note: this RR factor is used only when the ERPR
fine tuning factor is equal to 00h; otherwise, RR is
replaced by the ERPR dividing factor.
RR dividing factor
TR dividing factor
ST72334J/N, ST72314J/N, ST72124J
128
128
16
32
64
16
32
64
1
2
4
8
1
2
4
8
SCT2
SCR2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
SCR1
SCT1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
SCR0
SCT0
95/153
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1