HD64F2145 Datasheet, PDF (535/829 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

18.4.2 Control States
Table 18.4 shows host interface operations from the HIF host, and slave (this LSI) operation.
Table 18.4 Host Interface Operations from HIF Host, and Slave Operation
Other than
&6Q
&6Q ,25 ,2: HA0 Operation
1
0
0
0
0
Setting prohibited
1
Setting prohibited
1
0
Data read from output data register n (ODR_n)
1
Status read from status register n (STR_n)
1
0
0
Data written to input data register n (IDR_n)
1
Command written to input data register n (IDR_n)
1
0
Idle state
1
Idle state
(n = 1 to 4)
18.4.3 A20 Gate
The A20 gate signal can mask address A20 to emulate an addressing mode used by personal
computers with an 8086*-family CPU. A regular-speed A20 gate signal can be output under
firmware control. Fast A20 gate output is enabled by setting the FGA20E bit (bit 0) to 1 in HICR
(H'FFF0).
Note: *: Intel microprocessor.
Regular A20 Gate Operation: Output of the A20 gate signal can be controlled by an H'D1
command followed by data. When the slave processor (this LSI) receives data, it normally uses an
interrupt routine activated by the IBF1 interrupt to read IDR1. If the data follows an H'D1
command, software copies bit 1 of the data and outputs it at the gate A20 pin.
Fast A20 Gate Operation: When the FGA20E bit is set to 1, P81/GA20 is used for output of a
fast A20 gate signal. Bit P81DDR must be set to 1 to assign this pin for output. When the DDR bit
for P81 is set to 1, the state of the P81/GA20 pin cannot be monitored by reading the DR bit for
P81. The state of the P81/GA20 pin can be monitored by reading the GA20 bit in the LPC’s
HICR2 register. The initial output from this pin will be a logic 1, which is the initial value.
Afterward, the host processor can manipulate the output from this pin by sending commands and
data. This function is available only when register IDR1 is accessed using &64. The slave
processor (this LSI) decodes the commands input from the host processor. When an H'D1 host
command is detected, bit 1 of the data following the host command is output from the GA20
output pin. This operation does not depend on firmware or interrupts, and is faster than the regular
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