Operation - Renesas H8S/2100 Series Hardware Manual

Section 15 CIR Interface
15.4

Operation

The communication protocol of the NEC format is shown in figure 15.2. 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.
CIRI
Header
(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.
CIRI
[Legend]
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
Rev. 1.00 May 09, 2008 Page 442 of 954
REJ09B0462-0100
Address
Address
Figure 15.2 NEC Format
Header
A = 9.0 ms
Figure 15.3 Header, Address, and Command
Command
Command
B = 4.5 ms
C = 0.56 ms
Stop
Logic 1 Logic 0
D = 1.78 ms
C C