Renesas H8S/2100 Series, Hardware Manual

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Section 16 CIR Interface
Rev. 1.00 Apr. 28, 2008 Page 482 of 994
REJ09B0452-0100
16.4 Operation
The communication protocol of the NEC format is shown in figure 16.2. In the NEC format, data
consists of a header part, an address part, a command part, and a stop part. The TFM bits in CCR2
can select which data bytes to be stored in CIRRDR: four bytes of the address,
address
, command,
and
command
, or two bytes of the address and command. The carrier frequency is 38kHz.
Header Address
Address
Command
Command
Stop
CIRI
Figure 16.2 NEC Format
(1)
Header, Address, and Command
When a 9-ms high level and the following 4.5-ms low level are detected, they are recognized as a
header. For addresses and commands, when both of a high-level period and the following low-
level period are 0.56 ms, they are recognized as logic 0. When a high-level period is 0.56 ms and
the following low-level period is 1.78 ms, they are recognized as logic 1.
Header Logic 1 Logic 0
A = 9.0 ms B = 4.5 ms
C = 0.56 ms
C C
CIRI
D = 1.78 ms
A: High-level period for a header
B: Low-level period for a header
C: High-level period for logic 0/1 and low-level period for logic 0
D: Low-level period for logic 1
[Legend]
Figure 16.3 Header, Address, and Command