Rev. 1.0, 09/02, page 417 of 568
The SSU transmits serial data from the SSO pin and receives serial data from the SSI pin when
operating with BIDE
=
0 and MSS
=
1 (standard, master mode) (see figure 16.3 (1)). The SSU
transmits serial data from the SSI pin and receives serial data from the SSO pin when operating
with BIDE
=
0 and MSS
=
0 (standard, slave mode) (see figure 16.3 (2)).
The SSU transmits and receives serial data from the SSO pin regardless of master or slave mode
when operating with BIDE
=
1 (bidirectional mode) (see figure 16.3 (3) and (4)).
However, even if both the TE and RE bits are set to 1, transmission and reception are not
performed simultaneously. Either the TE or RE bit must be selected.
SSCK
Shift register
(SSTRSR)
Shift register
(SSTRSR)
Shift register
(SSTRSR)
Shift register
(SSTRSR)
(1) When BIDE = 0 (standard mode), MSS = 1, TE = 1, and RE = 1
(2) When BIDE = 0 (standard mode), MSS = 0, TE = 1, and RE = 1
(3) When BIDE = 1 (bidirectional mode), MSS = 1 and TE or RE = 1 (4) When BIDE = 1 (bidirectional mode), MSS = 0 and TE or RE = 1
SSO
SSI
SSCK
SSO
SSI
SSCK
SSO
SSI
SSCK
SSO
SSI
Figure 16.3 Relationship between Data I/O Pins and the Shift Register
16.4.4
Data Transmission and Data Reception
The SSU performs data communications using the bus with four lines: the clock line (SSCK), data
input (SSI or SSO), data output (SSI or SSO), and chip select (
SCS
).
The SSU also supports bidirectional mode in which the data is output and input using one pin.
•
SSU Initialization
Figure 16.4 shows an example of the SSU initialization. Before transmitting and receiving data,
first clear the TE and RE bits in SSER to 0, then initialize the SSU.
Note: When the operating mode or transfer format is changed for example, the TE and RE bits
must be cleared to 0. When the TE bit is cleared to 0, the TDRE bit is set to 1. Note that
clearing the RE bit to 0 does not initialize the values of the RDRF and ORER bits or the
contents of SSRDR.
Summary of Contents for H8S/2627
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