h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 592

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 17 Host Interface [H8S/2138 Group]
only when register IDR1 is accessed using CS1. Slave logic 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 processing using interrupts. Table 17.7 lists the conditions
that set and clear GA20 (P81). Figure 17.2 shows the GA20 output in flowchart form. Table 17.8
indicates the GA20 output signal values.
Table 17.7 GA20 (P81) Set/Clear Timing
Pin Name
GA20 (P81) Rising edge of the host’s write signal
Rev. 4.00 Jun 06, 2006 page 538 of 1004
REJ09B0301-0400
Setting Condition
(IOW) when bit 1 of the written data is 1
and the data follows an H'D1 host
command
No
No
Figure 17.2 GA20 Output
Write bit 1 of data byte
to DR bit of P81/GA20
Wait for next byte
H'D1 command
Data byte?
received?
Start
Yes
Yes
Host write
Host write
Clearing Condition
Rising edge of the host’s write signal
(IOW) when bit 1 of the written data is 0
and the data follows an H'D1 host
command
Also, when bit FGA20E in HICR is cleared
to 0