HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 626

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

In Serial Data Transmit Operations: In transmission, when transmit data is written to the
transmit FIFO by the CPU or DMAC and the TE bit is set to 1 in the serial control register
(SCSCR), the data is first transferred to the transmit shift register (SCTSR) in the order of writing
to the transmit FIFO, a parity bit is added by the parity generator (P/G), and then serial data is
transmitted from the TxD pin.
Each time data is written into the transmit FIFO, the value in bits T4 to T0 in the FIFO data count
register (SCFDR) is incremented, and each time data is transferred to SCTSR the value in bits T4
to T0 is decremented. The current number of data bytes in the transmit FIFO can thus be found by
reading bits T4 to T0 in SCFDR.
A value of H'10 in bits T4 to T0 means that data has been written into all 16 stages of the transmit
FIFO. If additional data is written to the FIFO in this state, bits T4 to T0 will not be incremented
and the written data will be lost.
When the transmit trigger number is set and transmit data is written to the FIFO by the DMAC,
care must be taken not to write data exceeding the number of empty bytes in SCFTDR indicated
by the FIFO control register (SCFCR) (see section 14.2.10).
In Serial Data Receive Operations: In reception, serial data input from the RxD pin is first
captured in the receive shift register (SCRSR) in the order specified by the RLM bit in the serial
status 2 register (SC2SSR). A parity bit check is carried out, and if there is a parity error the P
(parity error) flag for that data is set to 1. A stop bit check is also performed, and if a framing error
is found the F (framing error) flag for that data is set to 1. The receive FIFO buffer has a 10-bit
configuration, with the P and F flags for each 8-bit data unit stored together with that data.
Receive FIFO Control in Normal Operation
Receive data held in the receive FIFO buffer is read by the CPU or DMAC.
Each time data is transferred from SCRSR to the receive FIFO, the value in bits R4 to R0 in
SCFDR is incremented, and each time the CPU or DMAC reads receive data from the receive
FIFO, the value in bits R4 to R0 is decremented. The current number of data bytes in the
receive FIFO can thus be found by reading bits R4 to R0 in SCFDR.
A value of H'10 in bits R4 to R0 means that receive data has been transferred to all 16 stages of
the receive FIFO. If the next serial receive operation is completed before the CPU or DMAC
reads data from the receive FIFO, an overrun error will result and the serial data will be lost. If
receive FIFO data is read when the value of bits R4 to R0 is H'00, an undefined value will be
returned.
613