COP8SDE9IMT9/NOPB National Semiconductor, COP8SDE9IMT9/NOPB Datasheet - Page 42

• Manufacturer Part Number: COP8SDE9IMT9/NOPB
• Description: IC MCU EEPROM 8BIT 8K 48-TSSOP
• Manufacturer: National Semiconductor
• Series: COP8™ 8Sr

Specifications of COP8SDE9IMT9/NOPB

• Core Processor: COP8
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: Microwire/Plus (SPI), UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 39
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 48-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Data Converters: -
• Other names: *COP8SDE9IMT9; *COP8SDE9IMT9/NOPB; COP8SDE9IMT9

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8.0 USART
8.6 USART INTERRUPTS
The USART is capable of generating interrupts. Interrupts
are generated on Receive Buffer Full and Transmit Buffer
Empty. Both interrupts have individual interrupt vectors. Two
bytes of program memory space are reserved for each in-
terrupt vector. The two vectors are located at addresses
0xEC to 0xEF Hex in the program memory space. The
interrupts can be individually enabled or disabled using En-
able Transmit Interrupt (ETI) and Enable Receive Interrupt
(ERI) bits in the ENUI register.
The interrupt from the Transmitter is set pending, and re-
mains pending, as long as both the TBMT and ETI bits are
set. To remove this interrupt, software must either clear the
ETI bit or write to the TBUF register (thus clearing the TBMT
bit).
The interrupt from the receiver is set pending, and remains
pending, as long as both the RBFL and ERI bits are set. To
remove this interrupt, software must either clear the ERI bit
or read from the RBUF register (thus clearing the RBFL bit).
(Continued)
FIGURE 23. Framing Formats
42
8.7 BAUD CLOCK GENERATION
The clock inputs to the transmitter and receiver sections of
the USART can be individually selected to come either from
an external source at the CKX pin (port L, pin L1) or from a
source selected in the PSR and BAUD registers. Internally,
the basic baud clock is created from the MCLK through a
two-stage divider chain consisting of a 1-16 (increments of
0.5) prescaler and an 11-bit binary counter ( Figure 24 ). The
divide factors are specified through two read/write registers
shown in Figure 25 . Note that the 11-bit Baud Rate Divisor
spills over into the Prescaler Select Register (PSR). PSR is
cleared upon reset.
As shown in Table 19 , a Prescaler Factor of 0 corresponds to
NO CLOCK. This condition is the USART power down mode
where the USART clock is turned off for power saving pur-
pose. The user must also turn the USART clock off when a
different baud rate is chosen.
The correspondences between the 5-bit Prescaler Select
and Prescaler factors are shown in Table 19 . There are
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