HD6433044 Datasheet, PDF (275/867 Pages) Hitachi Semiconductor – Hitachi Single-Chip Microcomputer

9.7 Port 6
9.7.1 Overview
Port 6 is a 7-bit input/output port that is also used for input and output of bus control signals
(LWR, HWR, RD, AS, BACK, BREQ, and WAIT). When DRAM is connected to area 3, LWR,
HWR, and RD also function as LW, UW, and CAS, or LCAS, UCAS, and WE, respectively. For
details see section 7, Refresh Controller.
Figure 9-6 shows the pin configuration of port 6. In modes 1 to 6 (expanded modes) the pin
functions are LWR, HWR, RD, AS, P6₂/BACK, P6₁/BREQ, and P6₀/WAIT. See table 9-11 for
the method of selecting the pin states. In mode 7 (single-chip mode) port 6 is a generic
input/output port.
Pins in port 6 can drive one TTL load and a 30-pF capacitive load. They can also drive a
darlington transistor pair.
Port 6
Port 6 pins
P6 ₆ / LWR
P6 ₅ / HWR
P6 ₄ / RD
P6 ₃ / AS
P6 ₂ / BACK
P6 ₁ / BREQ
P6 ₀ / WAIT
Modes 1 to 6
(expanded modes)
LWR (output)
HWR (output)
RD (output)
AS (output)
P6 ₂ (input/output)/ BACK (output)
P6 ₁ (input/output)/ BREQ (input)
P6 ₀ (input/output)/ WAIT (input)
Mode 7
(single-chip mode)
P6 ₆ (input/output)
P6 ₅ (input/output)
P6 ₄ (input/output)
P6 ₃ (input/output)
P6 ₂ (input/output)
P6 ₁ (input/output)
P6 ₀ (input/output)
Figure 9-6 Port 6 Pin Configuration
9.7.2 Register Descriptions
Table 9-10 summarizes the registers of port 6.
Table 9-10 Port 6 Registers
Initial Value
Address* Name
Abbreviation R/W Mode 1 to 5 Mode 6, 7
H'FFC9 Port 6 data direction register P6DDR
W
H’F8
H'80
H'FFCB Port 6 data register
P6DR
R/W H’80
H'80
Note: * Lower 16 bits of the address.
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