207
GRC and GRD can be used as the buffer registers of GRA and GRB, respectively, by setting
BUFEA and BUFEB in TMRW.
The general registers are initialized to H'FFFF by a reset.
12.3
CPU Interface
12.3.1
16-Bit Registers
TCNT, GRA, GRB, GRC, and GRD are 16-bit registers connected to the CPU by an on-chip 16-
bit data bus. These registers must be written or read in 16-bit units; 8-bit access is not allowed.
Figure 12.2 shows the interface between the CPU and a 16-bit register.
Bus interface
L
H
CPU
On-chip data bus
TCNTH
TCNTL
Module
data bus
Figure 12.2 16-Bit Register Interface (CPU and TCNT (16 bits))
12.3.2
8-Bit Registers
The registers other than TCNT, GRA, GRB, GRC, and GRD are 8-bit registers, and are connected
to the CPU by an on-chip 8-bit data bus.
Figure 12.3 shows the interface between the CPU and an 8-bit register.
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