
22.6 Interface Specifications
The serial PROM mode supports two communication methods: UART and SIO. The communication method is
selected based on the first serial data value received after a reset.
To execute an on-board program, the communication format of the external controller (personal computer, micro-
controller, etc.) must be set as described below.
22.6.1
SIO communication
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Transfer rate: 250 kbps (Max.)
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Data length: 8 bits
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Slave (external clock)
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Hardware flow control (SO0 pin)
If the TMP89FM42 receives serial data "0x30" after a reset, it starts the SIO communication.
In the SIO communication, the TMP89FM42 functions as a slave device. Therefore, the external controller
must supply the TMP89FM42 with a serial clock (SCLK0 pin) for synchronization.
If the TMP89FM42 is not outputting serial data, it controls the hardware flow by using the SO0 pin. If internal
data processing is not completed yet, though data has been received, the SO0 pin outputs the L level. If internal
data processing has progressed to a near-completion state or if it has been completed, the SO0 pin outputs the H
level. The external controller must check the status of the SO0 pin before it starts to supply a serial clock.
22.6.2
UART communication
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Baud rate: 9600 to 128000 bps (automatic detection)
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Data length: 8 bits (LSB first)
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Parity bit: None
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STOP bit: 1 bit
If the TMP89FM42 receives serial data "0x86" after a reset, it starts the UART communication. It also measures
the pulse width of the received data (0x86), and automatically establishes the reference baud rate. In all subsequent
data communication transactions, this reference baud rate is used. For information on the communication timings
Usable baud rates differ depending on the operating frequency and are shown in
Table 22-4. However, there
is the possibility of data communication not working properly, even if a baud rate shown in
Table 22-4 is used,
because data communication is affected by frequency errors of a resonator of the external controller (personal
computer, etc.), the load capacity of a communication pin, and various other factors.
TMP89FM42
22. Serial PROM Mode
22.6 Interface Specifications
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