Acorn Products Z80 SECOND PROCESSSOR 409 用户手册
As can be seen from Fig. 6 and Tables 1 and 2, each numbered register
(e.g. register 1) is actually two registers, one for reading and one
for writing. The register selected is determined by R/W on the Post
system and by NRDS/NWDS on the Parasite system (see Tube Pinout
Diagram).
(e.g. register 1) is actually two registers, one for reading and one
for writing. The register selected is determined by R/W on the Post
system and by NRDS/NWDS on the Parasite system (see Tube Pinout
Diagram).
Only registers 2 and 4 are simple latches; register 3 is a 2-byte
FIFO in each direction and register 1 is a 24-byte FIFO from the
Parasite (Z80) to the Post, but a simple latch from Post to the '
Parasite. The Tube produces maskable and non-maskable interrupts to
the Parasite (see sections 5.6 and 5.3) and a reset signal (section
5.5).
The Z80 IORQ and M1 signals are decoded to detect an I/O cycle by the
OR gate IC22A, which provides the signal which, via the De-sync
circuit, initiates the chip-select, PCS, to the Tube. The Tube thus
occupies all of the Z80 I/O map, the four data registers and four
associated status registers reflecting throughout the possible 256
addresses.
FIFO in each direction and register 1 is a 24-byte FIFO from the
Parasite (Z80) to the Post, but a simple latch from Post to the '
Parasite. The Tube produces maskable and non-maskable interrupts to
the Parasite (see sections 5.6 and 5.3) and a reset signal (section
5.5).
The Z80 IORQ and M1 signals are decoded to detect an I/O cycle by the
OR gate IC22A, which provides the signal which, via the De-sync
circuit, initiates the chip-select, PCS, to the Tube. The Tube thus
occupies all of the Z80 I/O map, the four data registers and four
associated status registers reflecting throughout the possible 256
addresses.
5.10.2 Tube Pinout
Fig. 7 Pinout diagram for Tube IC